Jenny also carries the three-prong terminal body:
http://shop.sew-classic.com/Terminal...-SCE192797.htm
If the prongs on your terminal block are okay and it's a just a piece of the bakelite that's broken off, you can glue it back together with JB Weld 2-part epoxy and it will be very strong.
It will even fill little chipped areas along the crack and you can shave it level with an x-acto knife when it's hardened. It's black, so you don't have to paint it, either. :)
Great, I'm going to try this. My grandson works at Lowes so I'll get him to pick up some!! And use his discount, too!!! :)
I think I first found this stuff at Michael's, but Lowe's has it, too - up by the cash registers.