Finding the enfamil collapsible bottles was somewhat comforting. I used a few Dollar Store bottles like those before that but there was no comfort there. I've got another I found at WalMart by Outdoor Products that's a bit better than those Dollar Store bottles. It's a 1 liter collapsible and it accepts the Britta filters too.

All of the Dollar Store bottles I bought started leaking after a few days of backpacking. I hate tossing stuff after just a few uses.