Hoss, there's many places to buy what you're looking for. I use the 6" rolls a lot. The stuff will stick well and over curved areas you just push it down hard and the creases still stick fine. You can cut out your flames or anything right out of this stuff and it leaves no residue behind.
The attached image shows a hardbag with the bottom masked with the 12" stuff.
Any search for "roll mask" should help.
Good luck,
Phil