Sunvalleytek via Amazon offers the RAVPower 5,600mAh External Backup Battery Pack, model no. RP-PB03E, for $29.99. Coupon code "ZZEWKM9O" makes it $19.99. With free shipping, that's $2 under our mention from six days ago and the lowest total price we could find by $10. It features a built-in flashlight, auto-off, and compatibility with a wide range of devices (including the iPad, iPhone, and Android phones).