mk2 golf? worst door cards to trim in my opinion! I can sell you what ever materials you want to have a go yourself if you like.
few things, depending on how you're planning on doing this. you'll probably want a material with a decent amount of stretch in it. If you're trying to do it in one piece then it'll have to be very stretchy. if you do it in sections then to make it look any good you'll need a sewing machine. also the glue you need is a high temperature contact adhesive.
let me know if you want anything...