Your Sawyer filter problem was actually a Platypus problem; Cascade Designs changed to non-standard threads when they went to the newer curvy-shaped bottles. It also means that those of us who lose bottle caps frequently have to buy the new Platy caps; we can no longer use soda bottle caps as spares.

If you can find Evernew bottles, they make a much better choice for the Sawyer Squeeze. So can flexible soda or water bottles. I switched to all Evernew bottles because the cap is attached with a toggle to the bottle, so no more lost caps! They are of course in high demand because of their compatability with the Sawyer Squeeze coupled with Evernew's loss of production from the Japanese tsunami. If you find any available, pounce on them quickly!