What Kit said, or if you don't feel comfortable trying it yourself, I'm pretty sure an alternator place would do it for you. That, or maybe a local appliance repair place.

I just went through the same thing with a microwave. We DID get the magnetron replaced - sure we could've had a new unit for the same price, but why? This way we kept a little bit of money local, the labor costs anyway, and a lot of microwave out of the landfill. I think the repair guy thought I was crazy, but eventually I was able to talk him into taking my money.