I have a "ful" - expandable/contractable, small enough and big enough at the same time. It's a runner's camelback, basically, but very nice.
Looking at their website it looks like they don't make it anymore.
Edit: I fit a new battery, 2 bottles of wine and a new bike cover in this thing along with my regular carry-able stuff. It looks small but it fits plenty.
P.P.S. - It's about 7" wide - so no parachute.