I got mine from the home depot that was cutoffs or something. Sold it for 9 bucks,did both bunks and had a little left over for extra padding on the ends. Just ask the salesperson and they should be able to help or head over to loews for the same deal.
Did the same thing as ABOVE I got mine at LOWES. Just go in and say you need the marine grade carpet or astro truff. Saves you a TON on money if you ask a marine place.