Where can I get a new plastic gear?

one of the plastic gears broke is it possible to buy a replacement gear for a few bucks so I don't have to spend $50 on a new shredder? It is one of the gears that is actually two gears in one. The main gear is plastic and metal, and the broken gear is attached to that one and about a half inch in diameter. My shredder is a model number AS650C. Thanks