[Espeefan]

McMaster does have some gears like these, as already mentioned. I bought a set myself, but they get pricey, if you need a lot of them. McMaster has both nylon and metal gears, of various strengths. The stronger they are the more they cost. The other thing is most are either held with set screws or keyways and set screws. I don't know that I would trust a set screw, but maybe if the gear was pinned to the shaft instead, it would hold without slipping. Or at least you would need a flat on a shaft for the set screw to bite into. Some guys are able to score gears like these out of cheap hand grinders too. Sometimes it pays to look around.