If it's the black bakelite looking part in the second photo, I'm a bit stumped. I haven't heard this is a problem. However, It doesn't look as if it would be all that difficult to fashion out of metal. Maybe better photos of the broken part would clarify that If you have the plastic one for a template, try finding a local machine shop that could make it out of aluminum or could suggest another option. If it was metal, you'd never need to replace it.