Would it be possible, for those primitive sites that do get a fire going, to just put a clear plastic sheeting up over the cooking pot and catch the drip at the sides. Even an unbrella with cans tied to the tips might do. Boil the eggs, boil the potatoes, some of that moisture might end up in the cans. Umbrellas are designed to shed water, so the underside would do so too, and roll down into the tips holding the cloth taut, where tin cans could be wired to collect the drip. The handle is often metal, so would resist the fire when propped. If it were close to the pot it would be most efficient.
Offered by Nancy.
Might work - depending on conditions. If raining on the top side of a plastic sheet or umbrella then could be tricky to keep the good water separated from the rain water. Hot fires produce hot dry air and this will tend to melt plastic or at least dry out the under side. However, if the plastic or umbrella is far enough away then the air will began to cool before it gets to it. So under the right conditions it could work. Just as a tarp or plastic sheets made into a TP shape put over hot ground should cause water to condense on the inside and run down.
Offered by Mike.