They're Grandt Line parts and are made of Delrin.
Delrin being a trade name the material is Acetal.
Its famously non stick.
?
How skillful are you with a small drill because the proper engineering answer is to drill through the boss and axle and pin it with a bit of wire.
If you manage the hole then mix some 5 min epoxy to coat the wire as you push it it. Probably won't stick to the delrin but it'll stop the wire coming out
Paul Martin