a photo would help us know what you are looking at.
Guitar, Amplifier, and Korg Keyboard Parts | NATIONAL PARTS DISTRIBUTOR FOR KORG, VOX, BLACKSTAR. PARTS FOR FENDER, GIBSON, GRETSCH, HOFNER, SWR, GUILD, AND MUCH MORE would probably get it for you
A Antique Electronic Supply LLC probably has whatever it is, they have a large selection of sockets.
I'd be wagering it is a Belton socket.