Hello. Does anyone know a source for very stiff ~1/4" thick foam for the backpanel of a backpack. I'm not looking for the typical closed cell foam that seems widely available that you would use in shoulder straps or hip belts. The foam I'm looking for is frequently used in the backpanels of alpine climbing packs as it's stiff enough to maintain it's shape under heavier loads. It has essentially no give, doesn't like being folded in half and would be less than comfortable to sleep on. I've checked all the major online fabric sites (I think) so any pointers much appreciated.
Thanks so much!
