If you're looking for polycarbonate bottles (Nalgenes and others), I suggest you look locally. Postage etc. will eat up too many resources.

Yard sales, second hand stores, ads on local Craigslist and Kijiji, should yield all sorts of local sources. I have pulled a lot of these, brand new, for 29 cents, because most people don't want them. They're not used daily, but they are just fine for my many kits. A dose of bleach and a hot soapy scrub is of course recommended and SOP around here.

There are also a lot of stainless and aluminum water bottles coming into the surplus stream. I just picked up a couple for .99 each, with a promo message, never been used. Perfect.