https://www.proopsbrothers.com/pack-of-10-40-mm-diameter-plastic-cog-wheels-for-4mm-motor-shaft-60-tooth-gears-s7095-1692-p.asp
Pack of 10 40 mm Diameter Plastic Cog Wheels for 4mm Motor Shaft 60 Tooth Gears S7095
Pack of 10, 40 mm diameter plastic cog wheels for 4mm motor shaft, 60 tooth gears. Manufactured from plastic acetal for durablity and strength.