Sunvalleytek via Amazon offers the RAVPower 20,100mAh Portable Battery Pack for $49.99. Coupon code "DEA20100" cuts that to $39.99. With free shipping, that's the lowest price we could find by $10, although we saw it for $15 less in April. It features USB Type-C and Qualcomm QuickCharge USB 3.0 ports.