Don't confuse mil with mm. 8mm is nearly 3/8" thick. 8mil is .008" thick.
Most media that is self adhesive and printable is much thinner. You could achieve the thickness you need with an over laminate. I presume you are after the thickness for durability? Keep in mind, the thicker you go, the more difficult it is to conform to compound curves. Most vehicle wraps are 2-3mil with a vehicle laminate for durability and UV stability. I can certainly help you if you wish. Feel free to PM me.
Chris Haartwitter:@chrishaarThose who define design as knowing how to use Illustrator will be condemned to using Illustrator their entire career. - @monteiro