I often go out with my friends on long treks for 2-3 days. We usually carry bottles of potable water or chlorine tablets. Recently I bought Tata Swach Smart online. It was delivered to me within 3 weeks at no extra cost. It is really compact and light weight.
Very convenient for treks at it does not require electricity or running water. Just fill the upper tank with water and get pure water in the lower tank. That why I often use the word Purifier on the Go for tata Swach.