trailers parts department sells the seam-covering foam tape. Or you can buy it through a company like U-line. I think it's just a basic 3M foam one-side-sticky tape, with a highish bond adhesive.
Originally they used a similar tape, but with both sides sticky. They then brushed talcum powder on the "room" side to get rid of the sticky. There seems to be no reason to do that now with one-side-sticky tape available.
The other side of it is whether or not the Ensolite you are trying to get it to stick to is clean, or whether it could be contaminated with oil, silicone residue (from sprays, etc.), or just good-old dirt. I would make sure to clean it well first, perhaps finishing off with alcohol or another clean solvent (test first of course).