Hi, I agree that a gravity water filter that is light enough is a good way to go.

Sometime back in the summer of 2005 I bought a ULA H20 Amigo and tried that. It worked well but I did not like the filter that came with it. I also thought I could make one lighter.

This link will take you to my MYOG Gravity Filter thread at backpackinglight.com.
MYOG - Gravity Water Filter

ULA picked up my filter idea and they now come with the filter I used on my Gravity Water Filter.

This is sort of easy as a "Do it yourself project - MYOG"