I think a good combo for that would be to laminate a Heat Sheets emergency blanket to the Evarest pad of the thickness you want.
That minimizes bulk, and the Heat Sheets reflective material is more robust and resistant to tears than the cheap mylar space blankets.
Just cut the Heat Sheets reflective layer to fit the Evarest pad in the size you want.
They should probably laminate together well if you use some of that 3M Spray Adhesive, and be real good at laying it on the first time, because you'll only get one chance.
It may be best to use an oversize piece of Heat Sheets material, glue it to the Evarest pad, and then trim off the excess later.
They will roll up together in basically the same size as the Evarest pad rolls up to.
Theoretically, that should make a pretty effective combo for the thickness involved.
I personally would put the Heat Sheets reflective barrier layer on the bottom(with the silver side facing up toward your body and the orange side down facing the ground), because those things like to have a little bit of room between them and your body, to work best.
It would also protect the Evarest pad to a greater degree.