Enter the Fishpond Bitch Creek backpack.  It is a great size for my intended purposes, at 1,434 cu. in, and 11" x 8.5" x 20".  The pack is made of a cool new fabric called cyclepond, which is recycled commercial fishing nets.  Its a great way to reuse something from the fishing industry, and it has a nice texture.  The pack uses YKK Aquaguard #8 external water resistant zippers, has two external pockets for water bottles or fly rods (more on that in a minute), room for a hydration bladder, and a spacious main compartment.