I believe the Aquamira Frontier Pro is the lightest filtered water solution. I may be wrong.
Aquamira Frontier Pro filter
Many people use it, sometimes in conjunction with Aquamira drops, chlorine dioxide tablets, bleach, iodine, etc. It's not a pump style filter, rather it relies on gravity if used in an inline setup, or water can be filtered directly from the outlet through the bite valve. They're inexpensive and work for water that's not sediment riddled.
Tablets or drops used with a fine mesh strainer of some sort to remove debris is an even lighter option, but doesn't clear the taste of foul water like a pump will of course.