I've used 10-mil paper-backed for many years. I've bought almost exclusively from Tape-Ease, but recently a customer wanted samples and after two weeks following my request, I called TE and the guy found the package and said he'd send it next day. I asked him to ship it to the customer, and over a week later, the customer said: "no samples". Couple of days later, the samples arrived and they were incomplete and very small.
I contacted Sal at Monster WoodShop in of all places, Brooklyn, NY. NICE guy - sent me several 8 x 10 samples immediately and has no minimum order:
http://www.monsterwoodshop.com/I also contacted Formwood and they sent me several 8 x 10 samples immediately. Also, no minimum # of sheets order:
http://www.formwood.com/