Rear Mounting Bracket

Hello, I was tasked with trying to locate a bracket for a kitchen cabinet that is roughly 20 years old. Most places that I've checked only carry standard size. I need a pair right and left brackets that will fit drawer slides that are 1 inch in width. Oddly enough there isn't any identifying marks or numbers. all I do have is the broken piece. I would like any help that you can offer. Thank you in advance.