Hmm.. I don't use any binders anymore and can easily roll into shape with my hands, after seasoning and such, bake in the oven or drop into a liquid. I've done all proteins and they've all held up.
How big are you making them? Mine are usually not any larger than the size of a fifty cent piece. For a fat ratio maybe.. 85/15? Sometimes just salt/pepper, others I'll add aromatics and such.
Ok.. so... I wonder if you used gelatin if that would work, you know - the Great Lakes brand? I actually think that would be aces. Also off the top of my head to try arrowroot, tapioca or potato starch. GF flours. Maybe even smashed tuber as its on the dryer side. Smashed fine or run through a ricer, combined with the meat really well, then roll. My head is kind of thinking along the lines of gnocchi and how potato is utilized in there. Yes it has the eggs and flour but even without they hold up well. Sweet potato, too, as long as it's not a heavy moist one.