iMAXMADE via Amazon offers Prime members the MAXMADE 20,800mAh Portable External Power Bank, model no. MPB0004, for $33.99 with free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $6.93.) That's $56 off and the lowest total price we could find. It includes a microUSB charging cable and features overcharge, overload, and short circuit protection.