Anyone have a good (hopefully cheap too) source for buying individual billiard balls? I need a couple of particular balls for an effect I am working on, and an ebay search didn't yield any great results for me.

Why not drop in on a pool room and ask if they have any strays?

Worth a shot. I may do that. Thanks Pete.

Most pool shop will sell you one for about 10$ each
you can buy a whole set for between 40$ and 200$ depending on the quality you wish
for a magic trick, you don't need quality (by that I mean that you don't need the ball to be the most solid)
I guess you will make one appear and/or dissapear, so the ball does not receive a shock

If you have a wood working shop in your area, or wood craft store, they sell perfect unfinished wood balls for less then a $. Otherwise, how about these: http://www.magicgoods.com/MBallWood.htm a whole set for only $9. This is a good company, they give fast service.