The Husky brand HDPE "painters plastic" mentioned in the page Chris sent the link to has been tested repeatedly and passed Oddy tests consistently. Unlike most plastics you are used to you can handle the stuff all day long and never feel any kind of build up on your fingertips of the type that you usually feel using more common low density polyethylene - even virgin poly. I have used it as a contact material for many years with great success. For an image of the product click HERE.
I buy the 12' wide by 400" roll instead of the more common 9' x 400' version. I buy it at Benjamin Moore for under $18 a roll here in the bay area.