How much do you need to carry?
I LOVE my Nathan Intensity (smaller) and Synergy (larger but discontinued). They have a new women's vest called the Vapor Shape that comes in two sizes, holds only a 1.5 L water bladder, but claims 6.5 L additional gear capacity besides the bladder space. Looks just as comfortable, but I haven't run in it or even seen one in the flesh (fabric?). I've said before, 2 liters of water in my Intensity vest rides lighter and more bounce-free than 750 ml in my three-bottle belt.