rebuilding DC100A cartridges?

I've recently restored a DEC TU58 dual-transport tape system but am finding that 30+ year old DC100A cartridges are perhaps past the end of their useful life. The belts in many of them have rotted and broken. There are still some places you can get new cartridges, but they are more than $40 a piece. Has anyone found a way to source and replace the broken belts? I am not interested in preserving the data on the tapes as much as I am interested in just having working tapes... so I don't get ahead by moving a belt from a "good" cartridge to a bad one. I'm interested in trying to repair the bad cartridges. I've seen the writeup here, for the HP 9845 and its DC100As, http://www.hp9845.net/9845/tutorials/savetapes/index.html but that doesn't tell us what to do about broken belts other than to steal them from other cartridges... Chris -- Chris Elmquist