Our TRAK knee mills have had numerous problems with the drum brake actuation levers bending, and the cams wearing out. We are going to re-make ours out of a higher quality, properly heat treated steel (AR400). If you have one of these machines or another Bridgeport copy, you can mill your own replacement pieces out based on these parts models. Obviously this isn't a printer part.
dis-assemble your mill head according to the instructions in your manual. Make new parts. Install new parts. Enjoy properly working brake!