Sunvalleytek via Amazon offers the RAVPower Dynamo-On-the-Go 7,800mAh External Battery Pack, model no. RP-PB09, for $26.99 with free shipping. That's the lowest total price we could find by $9, although we saw it for $2 less four days ago (since expired). It features a power level indicator, dual micro USB ports, a wall charger, and carrying bag.