In the Aus Army Survival School (Darwin) they teach soldiers who find themselves with no plastic and no containers to dig a small pit (maybe 1/2 bucket sized), line it with paperbark or clay, fill cauldron with water, heat rocks as hot as possible, and using branches as tongs to drop hot rocks into water. Take off shirt, place on branch, hold in steam until saturated, wring out clean water. Very labour intensive but you need only fire, water and rocks. You can also condense that steam on the kicked-out windscreen of your vehicle, which will of course need to be supported at an angle over the cauldron but which will trickle the condensed water to the lower edge for collection.

Rgds
Bones