I can't say enough good things about the Overland brand Donner bag - the only downside I can think of is that I don't know if there's anywhere you can go to see one in person before purchasing. But it's got two outside spots for water bottles (deep "pockets" where the straps connect to the purse). It does have a flap over the outside pocket, but the flap doesn't cover the zipper of the main portion. There's a secure but easy-access lined pocket for a phone, which I loved as well. I got mine on EBags, might be worth taking a look.