Ha! I thought I was the only one who had broken bobbin cases like that! And I hope you didn't feel as stupid as I did.
I think that when you consider how old those machines are, it isn't a surprise that the metal i some areas is brittle. I just with I had thought of that BEFORE I tried to straighten it out.
There are new ones available from our beloved suppliers of old things, but don't forget that there are lots of "parts" machines out there, too. I had a couple of 99's that were beyond help, but the bobbin cases were fine. Believe me, I saved that part!