I'll be interested to learn how PU does in such a small part, as regards strength. Could it be something that grips very well on the lower wheel's post, but would still expand a little if need-be, so that sizing isn't as critical? How does PU take to cleaning solutions? Looking forward to your impressions after experimenting with it.I just had a thought with another possible solution that I hadn't considered previously. Polyurethane casting may be an option. I can do it on my desk with very little tooling and it should have the detail required for these parts.
I'll acquire some small amounts of the casting medium and some mould making material and try it out. I need some for another project and testing anyway.