You might want to try an easy solution that I have found very helpful.
Simply add some anti-slip tape on the inside of the ski, where the recessed handles would be - and even on the outside as well, if you like. This will ensure a safe grip when you carry the ski.
I use tape made for boat decks, stairs, etc. It is very durable and a cheap solution, so why not try it out?
Be careful though, if your legs are sliding on the tape while paddling, it will be very annoying.
I have the same 550 without handles.
/ Henning