Dehydrating your own is the only way to go.  You can do it in an oven if you don't own a dehydrator.  Pace salsa dehydrates really well if you are looking for a good commercial salsa to dehydrate.  Just be sure you do NOT buy the Thick-n-Chunky version as it doesn't dehydrate or reconstitute as easily as the thinner regular salsa.

Any salsa you make at home will likely dehydrate well, too, as long as it's a cooked salsa as opposed to one made with fresh ingredients and served uncooked.

Once you dry it (you'll end up with something akin to a fruit rollup from hell), just tear it up into small enough chunks to fit into whatever cups you use when camping.  To rehydrate in camp, throw some chunks into a cup, fill with boiling water and lid the cup with a scrap of aluminum foil (or the cup's lid).  Stir it up a couple times while dinner or breakfast is cooking and you are all set.  I don't worry too much about getting the exact right amount of water when rehydrating.  I actually try to use a little less than I think I need because thicker salsa is better than thin.  And if it's too thick, just add more water.

I'm sure Denton Doc will chime in too, when he gets back from his trip.