@boomerang,
I'd just find something like what I mentioned in the original thread -- a thin but sturdy-ish piece of plastic that you can then spray-glue the paper to.
Or you could maybe just do an outline with craft glue (along the outer edges of the plastic) to hold the paper on, with no adhesion in the middle.
I've seen the thin plastic stuff I have in mind at craft stores, Michael's and the like.
The plastic would be on the inside by the way, and from the outside it should just look like paper that's holding its form nicely.