The women's specific minimalist pack for 1.5 hours in th saddle.
Owner Reviews, Ratings, Comments and Criticism
I love it! I bought this as a solution to carrying water on long runs. To me the bouncing and sloshing is minimal, and definitely not a problem. I like that it has a small pocket on the front; it's big enough for my iPhone, a credit card and/or a little cash, and a house key. However, you can also put things in the actual backpack compartment (e.g. a Clif bar), although they'll be slightly harder to access. Overall I'm really happy with it.
Oh, and the description says that it's good for 1.5 hours of exercise; I think this is a pretty conservative estimate, although maybe accurate for hot weather. I'd probably be good for up to 3 hours with this (although I'd be drinking more water afterward).