@ DaveG - I buy vinyl in local car audio store, this material is widely used among car audio installers in Eu. It is very stretchy in both directions and it is very simple to pull out complexs shapes, especially if you apply heat to it.

You can also try this - take a piece of standard vinyl, wipe back side with accetone and pull backing off of the vinyl. now it will be super stretchy, but be carefull not to demage surface pattern.