If you want to carry a water filter around for basic travel, as opposed to days in the wilderness, one of the best bets is a water bottle that has a built-in filter. This way you're just carrying a regular water bottle around--which you probably would anyway in hot countries--but you just fill it up and go. Nothing to pump: your mouth does the work.
I used a version of this on three round-the-world trips and almost never got sick. It keeps you from having to have bottled water on hand just to brush your teeth and you don't add mounds of plastic to the world's landfills every time you need to get hydrated.
The Katadyn Micro Microfilter Water Bottle pictured here is $29.90 at Backcountry.com and that's pretty average. Sometimes you can find them on sale for less or different brands on a closeout.