REI-OUTLET offers the Platypus Origin 3 Hydration Pack Black, Blue, or Green for $29.93 plus $5.99 for shipping. (Free ship-to-store pickup is also available.) That's the lowest total price we could find by $11. This backpack comes with a 2-liter hydration bladder, twin waist pockets, and features a SlimeGuard anti-microbial reservoir, padded straps, tube clips, and more.