there's a radio shop right by the 2 truck stops at the I10 and Millekin (sp) in Ontario. the name is "Radio Shop" and they are known for being expensive, but i've been told they do good work.
there's also a CB repairman that works at the OutPost at 395 and I15. probably less expensive. he works out of a panel van parked just inside the north truck entrance. the name is "High Desert CB".
i don't have personal experience with either shop, but would probably try the one at the outpost first. there are a couple of other radio shops around, but i've heard bad things about one of them.