Suction cups

Where do you guys get those suction cups that pop into the film canisters to stick them to the side of the tank. Do they come in a package somewhere? I figured you'd have to drill the hole in the canister, but I can't find suction cups.

[Arklier]

Craft stores will have them to hang sun catchers and stuff. Anywhere that sells stuff that hangs on windows or sliding glass doors, in my experience. Just pull/cut the hooks off.

Lowes and just about any harware store should have them.