So far I have ordered all my headliners from companies that have the patterns and correct materials. I have seen shops that will purchase a premade headliner for a pattern and cut it apart to make a new one from a material that isn't available. This would also allow you to to a loose install to see what adjustments need to be made to fit the specific vehicle.

I've used carpet shield and it sticks great but almost too good. If it touches sticky to sticky it can be very hard to get apart without wrecking the pattern. The larger rolls allow you to cover an entire seat foam which is nice compared to the smaller rolls. It sticks to the foam very well compared to shelf liner which I have also used so I would list it as a tool in the arsenal to use based on the project. I am calling a sign shop this week to see about trying their transfer paper for patterning and also for paint protection. Two for one??

I paid $43.00 for one 4x8 sheet. I will look more but my local resources are pretty limited.

I just ordered a full 4x8 sheet of 1/8" HDPE plastic from Menards to be delivered to the store so I can pick up. It is the cheapest option that I have found. At my location they only stock 24x36 which was too small for the VW I'm working on.