Cellular Factory offers the 12-oz. 12000mAh Portable USB Battery Pack
, model no. 58036-HB-105, for $37.99
. Coupon code "1H0HUZ" grants free shipping
. That's the lowest total price we could find for such an item by $5, although we saw it for a buck less in March. It comes with several adapters suitable for most types of charging ports on portable devices.