I think if you start with the presumption of having clothing appropriate for the season you could add a tarp and/or bivvy sack for shelter, 50' of para cord, Katadyn MP-1 tabs for water and a canteen with cup and canteen stove, a GI spoon, some trioxane fuel tabs, 4 dehydrated meals, several high-energy bars, a Doug Ritter Personal Survival Kit, a had crank AM/FM/Shortwave palm sized radio, a Freedom II Photon flashlight, a survival knife of choice, a multi tool of choice, a wire saw, a good compass with map of area, and a decent Small sized FAK and you'd be back three or four days from now.

Some other things might be nice if space allowed: a better flashlight, extra batteries, more food, a Gerber folding shovel, and the list goes on ........