I switched from Platypus bottles to Evernew a couple of years ago because I was forever losing the Platy lids. Evernew has a plastic "thong" attaching the caps to the bottle, so I no longer have to carry extra caps. I'm really glad I made the change, because the newer Platypus bottles, whose threads were formerly compatible with soda bottle lids (which I could use as extra caps) and other fairly standard items, are now no longer compatible--including with the Sawyer filter. If Cascade Designs thought this a good marketing ploy, I beg to differ--they have lost me as a water bottle customer and I will no longer recommend Platypus, which used to be one of my staples. I also bought two 0.9L Evernew bottles to replace the bladders (essentially the mylar kind used in wine boxes) in my dog's Ruffwear pack. The Evernew bottles are much easier to fill and clean and the pair are 6 oz. lighter than the wine box bladders. There's no way my aging dog could carry a gallon of water anyway!
What I plan to do with my Sawyer Squeeze filter is to use one of my 2L Evernew bottles as the "dirty" bottle (marking a large "X" on both sides with a Sharpie) but take along the 2L Sawyer bottle as an extra water container, since it's lighter. It would appear (from home testing with the 1 L bottle) that the Sawyer bottle will work just fine for occasional use if I'm not squeezing it. Actually, it held up just fine for squeezing in my at home tests, but it does seem quite fragile for such continued stress.
Back in May I was able to get 2L Evernew bladders from Trail Designs. I got the 0.9 L size from a place up in Washington called the Great Outdoors Depot. The latter were out of the 2L size. It seems that Evernew's production was severely curtailed by the 2011 earthquake/tsunami.
Now that Evernew pots and pans are once again arriving from Japan, I assume the water bladders are available as well.