Van de Graaff generator belt

What is an easy to find material that I can use for my Van de Graaff generator belt? I'm making one for a science fair project. I tried using pantyhose, but I can't get it to turn right because it keeps going to one side of the top roller and getting stuck. I'm thinking I need something wider.

My brother and I built a large VDG. We tried using latex for the belt, but it didn't work well at all, now we have some blue exercise belt which works great. I recommend using a light colored belt, because some black pigments are carbon based, which would mess things up.
Good luck!
It rolls to the side because the rollers are misaligned.

You could try those rubber exercise bands they sell.
Yes, given a chance, your rollers should be slightly crowned as well as aligned. The rubber belt TUA suggests is a perfect material for you.

http://www.sci-supply.com/closeup.asp?cid=125&pid=259&offset=0 and
are sites with belts that you may be able to use
you can use fabric such as double sided vinal covered fabric that you can get at Michaels (sp?)
another option is to cover the ends of the inside of the van de graaff generator on the roller with thick tape, you should use vinal tape for the top (only about $1) or if you have problems with the bottom roller it will be metal tape (about $3) at ace hardware