Is this for your modeling hobby?
if so you could just go to Michaels and pick up some Frisket Film (basically the same thing) you can get a low-tack version too
if not you'd probably have to call all the medical/chemical lab supply stores and ask but then you'd likely have to buy in bulk (more so if you call a plastics company)
anachemia has been posted but there's also
http://www.caltechservices.com/ etc