[pct-l] backpack for carry-on

[Nathan Dreon]

Hi All,
I'm looking for a backpack to use as a carry-on, it doesn't have to be light, I willonly walk a few miles at a time.  I've been using a JanSport Big Student Backpack,34 Liters, it will hold everything I need for a few weeks but for long trips I wouldlike to be able to carry more gear.
Ideally I would find something that:can be used as a carry-on -- must have this~45Lno zipper on main compartment.A hip belt that takes some of the weight.Water resistant
Taller is better as it would likely make the hip belt more useful, my neck is troubled if there is too much weight on my shoulders.  It can have max dimensions larger than the allowed carry-ons as long as any frame doesnot make it too long.  It won't be full on a plane, no food/water, and almosteverything in the backpack will be crushable.
Does anyone know of a backpack that meets the specs?
Thanks,
Nathan