For the Contax, you can try
Mark Hansen. He seems to think very highly of Contax quality over Leica SM and Nikon rangefinder bodies. I haven't used his services though, but his rates are probably less than Henry Scherer's, I would imagine.
Isn't that 135mm actually the Sonnar in Contax mount? It sure looks like one.
I've got a Contax IIA, as well as a Leica IIIf, and I agree that the Contax is more user-friendly. If you get it serviced by a competent tech, you'll be good for at least a decade or more of shooting. I think one reason there are a lot of non-functional IIA and IIIA bodies out there is due to the fact that not as many people know how to repair them, and they're not well-known like Leica, thus not worth as much $$. Better shooters than the Barnack bodies, but were never quite able to compete with the M-mount Leicas.
Good Luck!