I have the same setup as Rob, having trialled a whole range of versions. One of my options is a stainless ring-pull quick release, the other as Rob has, some knotted cord. Both seem to work ok - even though the ring attachment looks a little bit clanky it works just fine.
Advantage - in event of some nasty you won't dislocate anything and as much as I can tell just get dragged centrally.
Where from: I got mine from the Paddling Centre mockepaddling.com however can't see anything there now (site soo sloooww to load atm).
Attaches like a belt with a quick release buckle.
Length - any leash attaches to the belt (large stainless D ring).
Only hitch I've had with the belt leash no pun intended has been getting caught up getting back into the boat. Had to get out in some messy stuff off Marina wall caught up in braid fishing line. I was a fair way off the wall in choppy stuff and the braid was floating but unseen. Anyway didn't have the heart to strip all his gear so got out and did the right thing (was caught around rudder). Anyway I found getting back into boat a bit messy with leash around my backside once in. That is I'd remounted port side without adjusting anything and the leash coming from my waist was on my right side as I swung up side saddle, so leash went from centre attachment around rhs side of my body to attachment on belt at front. When around your calf any tangle easy to adjust but not from waist.
Look that was pretty much a one-off so maybe it's just a matter of adjusting your kit before getting back in. I use waist leash either right out the back catching waves (not breaking onto beach) and as back-up in the car in case forgotten leg leash strap as on this day.
You're in Australia Colnagodreaming (hey try a Boardman AiR 9.8 dreaming) so give Whitworths a go
www.whitworths.com.au/main_itemdetail.as...e+&intAbsolutePage=1.
The quick release fitting is a snapshackle - prices and sizes ranging from $10-$60. The Ronstan below is Rolls Roycey stuff, spec'd way beyond forces we're dealing with. I have Ronstan gear but for paddling ones I buy $15-$20 max.