I like the one I have so much I bought a second. Wasn't a big deal tho - cost me all of 4 bucks.

I picked up a Swiss Army military surplus backpack from Herter's a couple years ago. Internal frame, holds about 1800 ci. It's a nylon weave coated with a dull green pvc material. Hasn't cracked or peeled a bit. The overall construction is super heavy duty, grommets and rivots all over the place, super thick leather straps and reinforced leather bottom.

When I saw the thing I decided to get another, and by then it was on clearance in the on-line bargain cave. I will admit it's a little heavy, but it is basically waterproof. Works for me.