I found a manual under the PB30. I was hoping the whole assembly had a part number, or a clue that would lead to someone maybe repairing them but it looks like each part is separate. The manufacturer of the assembly appears to be a company named Dixon and they were used about 10 years ago in quite a few units. I can find nothing on a source for any parts. The last price on the rebuild kit was about $275 - $300 so that seems a lot. Might be time to either make the parts or call around to the bone yards to see if anyone has the whole unit or used friction discs in working condition.
I have no idea how to make one but when i did a Google on the part many threads came up like yours and the people who solved the issue made their own. You would need to figure out what the material is, roughly the original thickness, obtain the material, use an old one to trace the part out, cut and use a dremel or something to cut them. Or if you have access to CAD you could draw it out in CAD to the specs a plasma cutter would use and take the file to someone with a plasma cutter to make four so you had some the next time.