I've used the PUR Hiker model to good effect in the application you describe. I also wonder if you've tried Aqua Mira? It should work just as well as Potable Aqua or Polar Pure, but it has no offensive taste.

I've used all the tools I mentioned, and the Aqua Mira is the most compact, best tasting solution given that you have fairly clear water to start with.

Bear
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No fire, no steel.