There is Ed Jefferies at Video Lab in Kansas, although I only have one experience with him and he wasn't able to repair it. I've heard good things though.
I'm planning to ship some stuff to a user named Cosmos (you can search and PM him here).
I'm not sure where he lives yet, but it's in Europe somewhere. I've seen him fix some pretty nasty problems that I would have written off.
Here is a thread he's involved in:
http://www.amiga.org/forums/showthread.php?t=57572I'm going to let him have a shot at the one Ed couldn't fix, among several other things.