Rev Jammer, Berkey had a 2.5 gal. on sale a week ago. It is a new system and takes out arsenic and more heavy metals. It came with two filters. The sale was on their website.
Using a tarp, with two ends tied to a tree, you can collect over two gallons of water, from just 1/10th inch of rain. This is using a small piece of tarp, not some tent! 1/2 inch, if memory serves, it can be 55 gallons. You can use the emergency sleeping bags, that are kept in cars (dirt cheap).
Drinking water needs to be number one on everyone's list. This method will also allow, what I like to refer to as "horse baths". Just thinking about it makes me want to go take a long, hot shower...