The 139Q is a great camera. I have one as well as an RTS, RTS II, a Yashica FX-2 and FX-3 Super 2000.
I agree with Trask that the Contax bodies are generally superior, but the Yashicas are not slouches and can be had for much less. The differences are usually in materials and not so much in engineering. The 139Q uses the same chassis as the FX-3. If you like the hair-trigger shutter release button on your 139Q, get another one ... or look at an RTS II for a bit more money. If you would rather get a reliable mechanical body for quite a bit less, I would recommend the FX-2 or FX-3 Super/Super 2000. I think the Yashica FX-D is essentially the same as the 139Q, as well, but I'm not positive. The FX-D also has a good reputation.
Alternatively, I can recommend Mark Hama here in the US to overhaul your 139Q completely. I'm sure he has the parts because I sent him a 139Q recently to use as a parts body (100 percent functional until I dropped it and the mirror came loose!). The price for the overhaul and minor repairs is usually $140 USD which comes with a 6 month warranty. I've had two cameras repaired by him including my RTS, which works like new even a year later.
You might also google Rockycameras in the UK. Contax Yashica bodies can be found there for good prices. He's got some bad reviews on the web for slow shipping, but I've always received what I've ordered albeit many weeks later (of course, i'm across the pond).
Glad to see another C/Y "shooter."