I recently bought a Timbuk2 Commute in large. The bag is waterproof and it has a very large capacity. In my opinion, if you need more capacity than this bag provides then you should probably just carry a backpack or use panniers. It's a great bag and it sounds like you could use the space. It only has one water bottle holder on the outside (though there are two inside). It also has slots for 2 tablets and a laptop. I'm happy to answer any questions.

Oh, its a little outside your price range but i'm sure you could find it on discount at one of the outdoor retailers.