Naphos via Rakuten Shopping offers the New Trent Dual Port Smartphone Charger 5,200mAh USB External Battery Pack, model no. IMP50D, for $19.95 with free shipping. That's tied with our September mention and the lowest total price we could find by $13. This backup battery pack charges up to two devices at once. It includes a USB cable, microUSB tip, and miniUSB tip.