Could you print pedal caps. These get lost all the time, especially Shimano 600s. I personally have three sets with each needing caps and they can't be used. I would cannibalize rough sets at the co-op but in the Covid world that's out.
If you can make them, I'd post on the sales forum under c&v. Also, downtube shifter boss covers for the Cyclone and Shimano single post mounts that allow bikes to switch to brifters or barcons can run over $100 for used ones. There's a market for those also