You want a daypack, need a laptop backpack and a hydration pack. Three different Crumplers is one option. The three-in-one Yee Ross is the other. The flexible and compact Yee Ross holds a 4-litre hydration bladder or 13" laptop in a rear sleeve, your tunes in a centre zippered pocket, and your stuff-du-jour in a 13-litre general cargo space at the front. It also has dual external zippered side pockets for those things you want to keep close at hand.