Replying to Ski building question (Vacuum Press)

I recently began to build a vacuum ski press. However, after creating the mold for the skis, I ran into a problem. I didn't know what I should use for my vacuum bag! IS there a special type of bag I should buy? Should I just use a regular plastic sheet? All of these questions, but no answers... I've looked around on the internet but have yielded no results. If anyone that has built skis can help me out that would be great.

P.S. What type of epoxy did you use for the skis you built?