This Ozark Trail 40L Crestone Backpack drops from $38.76 to $19.99 at Walmart.com. Shipping adds $4.97 or is free with ShippingPass (get a free 30-day trial). This is the lowest price we could find by $7. It is compatible with a 30-liter hydration pack, features a air mesh padded back panel, shoulder straps and waist belt, and has multiple exterior gear attachment points. Sales tax is charged in most states.