Enjoybot via Amazon offers the Enjoybot 10,000mAh Power Bank for $27.99. Coupon code "BVCIYDQV" cuts the price to $17.91. With free shipping, that's $41 off list and the lowest price we could find. It features dual input and output ports and a type-C charging cable. Deal ends December 31.

Update: The price has dropped to $24.99 before coupon, $15.99 after.