Hi there,
I've been looking for the same thing. I'm in Brizzy and there were 5 (count 'em - 5) guys that would do this sort of thing. 4 are now retired or only do leica/Contax/FSU cameras. The last one (the name and contact of which I'll give you if you're interested) maintains he's pretty darn good with it all. Will recalibrate the GIII for a 1.5v silver cell, CLA, even machine new parts and re-silver rangfinder mirrors if needed. When I talked to him (about a year ago) the cost was about $100 - $130 (AUS) for the full monty.
I had a (minor) falling out with him (over a 'free' quote on a C35 - that he wanted to charge me $30 for..) so I never put my GIII through there. But I may have to eat crow and give him a call because there seems to be no one else in this neck of the woods that will do it. They've all gone over to fixing gameboy's. (digital).
however, if you are interested, yell.
best,
David.