That's what I've done, and although it's not a solution I am entirely happy with, I've not figured out better.

One of the things in my BOB is a 5 gal bag for water, which I think is made of mylar, like this: http://beprepared.com/product.asp_Q_pn_E_ZA%20B100_A_name_E_5%2DGallon+Mylar+Water+Bag

I can carry it much easier than I can ever a pint of water.