Ok, the stuff we use is "spa liner" also known as "weblon."
It is a nylon or dacron impregnated heavy duty vinyl, on the outside layer. Then a high density soft sheet foam similar to thin-su-late for the center core. Finally, the inside layer that you see inside the camper is a heavy duty nylon pack cloth. Then you have a bunch more special materials, when you start looking at the windows, screens, vel-cro closures, threads, and sealants... It's kind of more complex than it looks at first, unfortunately. That is why we have to charge about $1,000 for a new complete, 4 window, insulated liner, ready to install.
If you do want us to make one up for you, just need your camper brand name, model, your overall size, and how many windows you want.... oh, and the money.
Let me know, thanks! Rob