EVA, ethyl vinyl acetate. 2-3 mm sheet is what I used to use. Personally I don't bother any more. I'm sure that's what is used and it is heat moulded to whatever shape or pattern is required. The thicker densities are heat mouldable.
Just get the real thing from Think, I am sure they sell foot pads.
You will end up spending more time and money stuffing around with the wrong stuff, and then giving up as stated in previous post.
Personally cannot do leg drive without the pads as your feet slip.