FWIW: I keep hooded TyvekŪ "moonsuits" in vehicles and primary ready packs. They are deliberately sized overly large for several reasons. A TyvekŪ envelope, repeatedly crushed and fluffed (by hand) turns into a flexible and tough bag to stow a tightly rolled "moon suit" - the self-adhesive flap serves multiple purposes if cut off and used as a piece of TyvekŪ repair tape. The whole bundle gets bound with 2-3 ranger bands from a fat-tire bike inner tube.

Very lightweight, compact, and versitile/adaptable bit of "spare clothing" for a very low cost (in case-lot purchases).