US Rexs via Amazon offers the Ameiseye 20 Liter Internal Frame Backpack in Green for $40.53. Coupon code "LRAAF39O" drops it to $29.99. With free shipping, that's $40 off list and the lowest price we could find. Features include a mesh back panel, cushioned shoulder straps, hydration compartment for 3 liter water pack, and water resistant rip-stop nylon.