These are offered for sale fairly regularly on EBay under the Crafts/Framing section, although usually in the larger sizes. The size you are looking for would be small for a vacuum press.
At xmas my wife purchased some 4 inch wide felt which is tacky on both sides. This is sold as Christmas card hanger. I cut this into strips and stuck it to a piece of ply that I had roughed up a little with sand paper. Paper will stick nice and flat to the felt, best of all the paper peels off nicely, its well worth a try.
Thanks all for you comments. Dave I will be sure to check out ebay. W Hume those exposure units look like just the thing i am after, now I will have to save up for one of those.