Just head down to the hardware store. It's standard washers and a standard sized screw. I want to say it is a 1/4 inch screw for a t2i, but I'm not positive.
If you want to have fun when you are down there, go check out the lamp section. You can find replacements for the screws that are used to balance and attach the top plate (brass thumb screws) and they will be cheap and great to have around for glidecam emergencies.