You can find backplates for eletrical boxes that would look right and work from numerous electrical supply places. a few places to check for things is Antique Radio Supply which is an online store, and they have a catalog. the store and catalog came first, they’ve been around for a long time. They sell stomp boxes and kits, and parts for effects, amps, guitars.. just measure the size of the plate you need, and see what they have that might match. they may even have the exact thing, or a close copy. i think their ul is something like http://www.tubesandmore.com and another store thats good for electrinics things online, for guitars and amps, effect and more… is Mouser.com -they had the IC chips my old 1980 Peavey amp needed, the exact same ones, same name brands and everything, and they were cheap! (I replaced about 17 chips and it was under ten dollars for all of them.) the backing plate is such a simple thing; you could also get one from another electrcnic thing.. or just get a small piece of metal that matches at a hardware store, or junkad or anywhere you can buy some clean flat metal. if its not the exact size, you can cut it yourself, or have a local tradeschool cut and make you one thats perfect. They often do little repairs and things for a small donation.