I bought a box of elbow length polyethylene gloves from G&E Pharmacy for 12.50. They are kind of thin, and won't last long, but the box has 100 gloves in them. Its been working for me.
Other than that, you could just get gloves from J&L. Several people use those. Only complaint that I've heard of is that it can be a bit clumsy using those since they are a bit thicker, and most people only use one glove while working on the tank... so the other glove is wasted. If you're right handed, maybe find a left handed person and split the cost?
-Richer