I am a fellow bike tourer. Generally you will get adequate water from approved sources - campgrounds and the like. On occasion I have obtained water from open streams. My preferred treatment is to boil. For backup, I might consider some type of chemical treatment. I would not lug my filter along.

With a good hot stove (Pocket Rocket) boiling is surprisingly quick and easy. I bring the water to a rolling boil, decant into containers, and proceed to the next round.