GPS, again...

I am looking for a very basic GPS, preferably used. 
I know GPS has been discussed ad nauseam here, but surely one cannot rely too heavily on dated technology reviews.  I have been surfskiing for a decade or so, entered many races, but have never had any electronics other than my watch.  I am fine with that setup, but have been thinking I would not mind knowing my estimated speed occasionally.  I may or may not use it much, so do not want to spend much money on it.  Used is preferable, if used is reliable.  I want it as basic as I can get it.  I do not want bells and whistles beyond current speed.  Average speed, max speed, distance traveled, and elapsed time would be nice, but not mandatory.  I will not use any other feature.  I will not care to see my path or enter data into a computer.  The fewer things to break and suck battery life, the better.  I want the face to be big enough to read from my foot straps, so no wristwatch size.  Good battery life, easy to gain signal.  What is my best bet, where, and about how much?  Thanks.

A good bet might be one of the older Garmin Forerunner 300-series watches, they were huge and hence the display was relatively large.
I just bought a Garmin Edge 130, which is the newest smallest cycling GPS. I like the fact that the display is large, so I can have 5-6 stats showing, all of which I can see without much effort. Plus the display is excellent in full sun. I also didn't want to spend a ton: $200. I have a Bluetooth HR strap and cadence sensor, so I didn't want to get an older Edge. Main downside is that the waterproofing is touchy, time will tell. I taped over the barometer and beeper holes (which should be waterproof) and applied quite some grease to the USB port cover...
There are some cheaper no-name cycling GPSs, if you can find one that is waterproof that might be not bad either...

Have you considered using a smartphone in a dry bag along with an app such as Endomondo. This will give you all the information you require and accuracy compares favourably with my Garmin and Suunto watches. There is a good display which you can see if you attached to your footstrap. Personally I keep it in my shorts pocket and listen to the announcements which I have set for every 200m. Keeps you in touch with what you're doing without having to focus on it and provides a full recording including map track of the activity.

Phone works great for recording whilst stashed into the PFD. But then you get zero real-time feedback.
Mounting it on the footstrap is a disaster, IMHO. After an hour of GPS and screen use the battery will approach empty on most phones. Drops on the pouch periodically change the display, even if you use some degree of ballooning. I can't count the number of times I've had to hit the back button or drag down the metrics display in the Endomondo app. Trying to manipulate the app is pretty sketchy and distracting due to the water drops on the pouch. Even if your phone's screen is "OK" in full sun, by the time you put it into a plastic pouch which inevitably gets salt stains the readability becomes awful. A big part of the value of the phone in the PFD is that you can call for help if you loose your boat, if the phone is on the footstrap, well, good luck! Can the phone stand-in if you forget your GPS: yes, is it a good solution? I don't think so...

As I said earlier, I don't use the display on Endomondo. It all depends on what you want from the metrics presented. I use a Garmin Fenix 5 and an iPhone running Endomondo on a daily basis and tbh the only thing that I get from the Garmin over Endomondo is a measurement of cadence. I don't look at the displays as I get enough information from the sound bites which both devices provide. Lap number, heart rate, lap speed, distance travelled: announced every 200m or 250m are sufficient information for me to manage my paddle. you can even set up Endomondo to read out pre programmed intervals if you want. You can analyse both to your heart's content once the activity is over.
For someone who already owns a smartphone and wants basic data at a low cost, Endomondo is ideal and covers all the metrics mentioned by the OP/

I use a garmin 310xt , bought used / almost new condition on ebay for thirty something bucks.  Could go for an even older generation if you want simpler and cheaper.  After a 4 hour paddle still has half the battery life left.  If you only have 1 data field on the screen, for instance speed, the numbers are really big.  If you have 2 fields like speed/ HR still pretty easy to read unless there is glare.

Second hand site we have in Australia among others is Gumtree, think it might even be international. Anyhoos just bought a Garmin Edge 1030 to use in the boat and on my bikes for $350 (hasn't arrived so can't comment o the product) however have bought lots and sold a fair bit on Gumtree and have had no probs - absolutely preferable to eBay - some shitty sellers there. Two buys I spotted good value below. I've had them both and vouch positively for them. (In my top drawer is one unused Garmin 735 - heart rate measurement is absolute crap so don't bother - later model doesn't mean better model!) , currently have a 920XT as my daily watch,  is model above 910 but sama sama - and a brilliant watch though way above your basic requirements. As an aside however, despite what you think your needs are I would buy at this end of available technology. However $30 for the Foreunner310 XT a la PSwitzer - Patrick's above -  if not this one, snap one up wherever you can get it. Just do a Surfski.info search and this model rates highly. 
Garmin Forerunner $30
Garmin 910 XT

Garmin Forerunner 25 is basic enough and cheap enough used. I also had a Forerunner 110 which was fine too but it died after a year. Suppose it was just too old of a unit. 25 can be found used but fairly new.

I use Garmin Foretunner 25. You can buy them new for as low as 70.00 USD online. Simple to use, and a long battery life that is rechargeable.

Cerca Trova wrote: I use Garmin Foretunner 25.

Interesting.. I would expect your surfski to sink with a 4-tonner jumping into it

Seriously, that looks like a decent price point if you're OK with a watch form factor, it has its pros and cons. I would not expect rapid GPS updates given the claimed run-time vs. how small the battery must be...

I just tried a $14 cadence sensor with my Edge 130 and it worked like a charm! Next step is to set up a field to display distance per stroke... I think I need to change my handle to paddlenerd

Thank you very much for the great, useful info.  It looks like Garmin is the most popular.  I used to use Garmin handheld's for offshore fishing 10-15yrs ago and they never seemed to last more than about a season before they would not lock in on satellites, or power off midstream.  I cannot help but think they have gotten much more reliable, especially since nobody here complains of this.  The ForeRunner 310XT seems to be the closest fit for our sport (triathlon=water, wet).  I will try a refurbished one of those and if I like the idea of having a GPS in general, I may look to go bigger and better.  Thanks again.