Based upon the research I did for my own EDC/GHB, i would recommend that you use either or both of the Seychelles "Advanced" straw or bottle purifiers. Light and compact, with very good, test data and on-line comments. BIG BUT, I have no first hand experience with either. I also carry the Katadyn tablets and the Survival Resources Water Bags and their little fold up funnel to hold coffee filters, to pre-filter. The Katadyn Purifier Bottle, ES version, also gets great write-ups. Its a bit bigger and more strongly constructed that the Seychelles bottle, but heavier.