Latex would be possibly, since they used it for the hand guards
Some with plaster bucks could easily apply a skin of latex onto the bucks.
Put the tigh mold into a box, fill it up with latex, and wait for an hour.
Pour the latex back into the container, and voila, your have a 2 mm skin of latex on the buck.
Before anyone asks: I won't do it, because I don't want to sculpt thigh armor and recast those parts is out of the question.