Check your local craft stores. I have found a variety of items like these - though not in such large sheets. Not sure what they are using as 'backing' but is a bit of a pain to work with but can be made to look quite good.
BUT MATTE SEAL FOR CERTAIN or you will be dripping crap all over the place, top and bottom. I actually glue my pieces to wooden bases so the bottom seal isn't necessary but the top seal sure is.