Why not use the Nalgene Bottle itself? It's not compact but it is easy to carry (tons of different carry options). You can store your gear in ziplock/glad freezer bags inside the container so they're good to go if you have to empty the bottle for use as water storage.

Another option are these http:

http://www.basegear.com/lmwaterpouch.html

I just received some and they are far superior to the aloksaks (which I also received in the same order) I blew air into one of the liberty mountain pouches, sealed it and stood on it. The bag didn't let go. That test didn't work with the aloksaks, in fact the seals on them don't work well at all.

I think these are cool as well, little off topic but great water storage

http://www.msrgear.com/hydration/dromedary.asp

or

http://www.msrgear.com/hydration/dromlite.asp

Again not compact but easy to edc.

JMO

BTW not affiliated with any of the above mentioned.

Blitz