You could also pick up some POLYSTYRENE TUBING with the right inside and outside measurements, cut off a bit on one side, slip it over the axle and glue it down. Most Hobby Shops carry a brand of this and is not very expensive. You could then color it black with a permanent marker.
https://evergreenscalemodels.com/collect...rene-tubes
https://evergreenscalemodels.com/collect...rene-tubes