Any sources for the power switch on a Belles 350A?

I would try David himself. Another person you might try is Rich @ Signature Sound in NY. Rich does some warranty work for David, and also some individual Belles repairs. Worth calling him and asking. Do a search for Signature Sound, I’m sure you will find the phone number.

https://powermodules.com/contact-us

I wouldn’t expect David to reply via his web site. Better to try calling, but even that is a crap shoot.

Probably have better luck with Rich at Signature Sound….or, maybe Johnny Rutan at Audio Connection. Johnny talks to David regularly.

i agree with calling david belles

in the two times i reached out to him, i called the number during east coast working hours and he answered himself both times...