Wet Bath Floor

We had nothing on the floor until we were camping mid-October last year and the floor felt cold. We had part of a roll of the foam stuff that we also use on the bottom of all the cupboards, the anti-slip foam. I simply cut a piece of it to fit. Warm enough floor and because the Bigfoot floor is smooth fiberglass, the anti-slip is nice as well.
I bet that you have at least one part roll of the anti-slip foam around somewhere.
Brian