You might want to try Authorized Photo Service in Morton Grove, Illinois. They used to be the Nikon service center for the Midwest. Good folks, they've done work on rangefinder lenses for me in the past, as well as Nikon SLR bodies. A number of years ago they were still working on Nikon S2 rangefinders, not sure if they still are, but worth a call. (847)966-4091.
Also, you are in Wisconsin, I'd talk with Don Goldberg of DAG Camera Repair. He's in Oregon, Wisconsin and he's does top notch work on all types of rangefinders. He specializes in Leica, but also does Nikon and Contax rangefinders. He can be a little busy, and therefore hard to reach, but you might want to give him a call (608)835-3342.
That should give you a place to start.
Best,
-Tim