I buy most of my clips from Ace Hardware & OSH.

BTW, if you are taking the clips off or putting them on without having spares immediately to hand, then you may want to use the following trick: get a 1 gallon Ziploc bag and put that over the entire assembly, then put your hand inside the bag to work on the gear. Since the bag is totally seethrough you should still be able to work inside it quite easily, and if the clip shoots off the axle it will be caught inside the bag for easy retrieval.

Gordon