REI Duck's Back Rain Cover - 20 Liters - $12.93

With a waterproof polyurethane coating to keep out the rain, the REI Duck's Back 20 backpack cover lets the elements roll off your pack even if you're not a duck. Drawstring shockcord with toggle lock securely cinches around pack for a snug fit. Zippered storage pouch doubles as an accessory pocket to stash small essentials; offers a vertical strap for easy securing or belt clip for quick horizontal attachment. Cover has bottom drain hole for release of trapped moisture. Pouch dimensions: 5 x 3 x 1.5 in. - $12.93