I'd also suggest the Fast Snaps, but find a few locally and see if he can make them work before you buy a bunch. They are pretty small.

If that's a problem for him, either go 'loop to loop' as Rainbow Chaser recommended, or try a Duo Lock Snap...they are just light wire, and the small ones are small enough for subsurface flies...probably okay for larger dries too, but not those 16s or 18s.

Buddy