There is a woman in the MZ DLC that has 100% repair skill. However, I suggest you increase your own repair skill to 100, as you can't really rely on anyone for long.
The woman in MZ disappears. There is a man who owns a store (forgot his name, I think it's Harley or something) in Point Lookout who has a pretty good repair skill, and he can't be killed by anyone but you, since he's indoors and enemies don't go indoors. Also, he says the locals there aren't hostile towards him or something..