^^ (above) Ah, that plastic is acetal or delrin, yeah, I would not hesitate to use that plastic, it's one of the tougher ones, they make ski bindings out of the stuff. But I also like the design with aluminum separated by a thin copper sheet and a touch of lube. It works, and has a graceful and slow degradation/failure mode.

I don't know about bronze being self-lubricating, but there are tons of applications of "DU" bushings, which are metal backing, porous bronze layer, and then coated with PTFE that impregnates down into the porous bronze, very common and durable if not contaminated with dirt and such. A piece of one of those cylindrical bushings in place of the original copper sheet, would be superior, and not require lube.