it doesn't take much weld to keep the pickup from falling off. Any machine shop should handle it. You can even mig weld it but my advice take out all the guts first, espcially the pressure spring. You just need to have it tacked not a full 360* weld.
To bad so far, Im not good but cheap. And a mig welder will work just fine, like 6nova4 said, just tacks, maybe three good hot ones. Use some acetone to completely dry out the metal, oil will be in the pores. Do a USPS flat rate box mailing to me and Ill weld it up nice. JR
I haven't needed any welding done in a few years, but Lenord always did a great job for may various (smallish) projects. He's off Fender ave in Fullerton. If you're interested I'll dig around and find his contact info.