If there doesn't seem to be an obvious solution or answers, that would be my course of action.
However, that type of motor mount is quite common in my experience. I would venture to a motor repair shop that services all brands of motors and stayaway from "Delta Service Centers". My local motor repair shop is 40 minutes away and last time I was there I saw about 100+ motors on shelves and on the floor all over the shop. All sizes and brands. They sorted out my wiring issue in less than a day. Very knowledgeable folks there.
My Compressor Duty Craftsman motor has that type of mount:
From an Ebay listing:
Maybe a source for new brackets here: