Patuoxun via Amazon offers the Mpow 12,000mAh External USB Battery Pack in Silver or Black for $38.99. Coupon code "PB31MPOW" drops it to $29.99. With free shipping, that's $36 off list, tied with our February mention, and the lowest total price we could find. It features dual USB ports and a 10.2-oz. weight, which is less than most similar devices.