We have talked about this before, it is a very important problem.
Researchers at MIT have come up with this portable desalination device. Hand carried, does not need a filter.
It doesn’t produce a lot, only a cup and a half an hour, but that is enough to keep you and possibly two of your friends (depending on how big you are) alive. 9 watts is small enough that you could keep it going indefinitely (with enough extra to keep it going at night) with a 2ft X 2 ft solar panel. But you need 40 liters of seawater to get a liter of desalinated water.
I’m anticipating that every ship and airplane will eventually have some of these, and they will be available to hiking expeditions and such.
The article says cheap, but I guess that is all relative. The starting price will be about $1500.