Call Top Shot Armory and see who they recommend. Other than Belchers in Mishawaka, I don't know of any others around. But I haven't had a need for one either.
He opened a shop out by the Hummer plant. It's called Belcher's Gunsmithing at 13398 McKinley. He's done some work for me. I've been happy with the cost and timing. Phone # is 703-3811.
Good luck.