One day while carrying a heavy load of groceries, my shopping trolley took a tumble and shattered the plastic bushing in one of the wheels. I designed a replacement in Fusion 360. The wheel was originally held in place by snapping into a notch on the end of the axle, but I doubted the durability if I tried to do that, so instead I added a U-shaped clip to retain the wheel. This piece is then secured to the axle by smaller clips that are superglued in place.
I printed this in Nylon 6 for its strength and low friction. This nightmare filament has heavy warping and bad stringing, and I'm stuck with a kilogram spool of it. Don't be like me, if you want to try printing nylon then spring for a Taulman product.