The exact same happened to mine as I installed the carb back in after I overhauled it. It is made of plastic or backelite though. You might try to repair it with those heat glue or plastic guns?Here are pics of the old one and the "new" one I got. The old one had its "ear" broken off. I might be able to salvage it by JBWelding it.
I tried with 2 component epoxy glue, but it didn't work.JB Weld does work good on those cast parts. Would sure be worth a try.