What's wrong with the shutter? This link pulls up some YouTube videos by Chris Sherlock on repair/overhaul of a Prontor S, which is what I think this camera has.
prontor shutter repair - Bing
Don't get me wrong -- I'm not saying this is for the inexperienced or faint of heart, but it might give you an idea of what's involved. (And if it's just a matter of the shutter hanging up at some speeds, I've found the Prontor shutters often respond to some lighter fluid judiciously applied. I know that's a Grade C approach, but it has been effective for me on more than one occasion.)
Others will I hope have their own suggestions. But first, what is the issue?
To answer your initial question, there was a place, Flutot's, in California I think, that specialized in shutter repairs -- though 1) I'm not sure they're still in operation and 2) they tended to concentrate on large format shutters.