I just got back from a 4 day backpacking trip with a new cycling friend who brought this product call Aquamira. It's two small bottles of liquids that when mixed together in about 7 drops each makes a tasteless way to purify water in the back country.
I just looked it up online at: http://www.aquamira.com/products/aquamira-water-treatment-drops/
Comes in two small bottle weighing just around an ounce.
I plan to get some asap for my next out door adventures