Amazon offers Prime members the Lumsing 10,000mAh 3 USB Port Power Bank in Black for $16.99. Coupon code "KIZ26NMB" cuts it to $12.74. With free shipping, that's $15 off list and the lowest total price we could find. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $5.99.) It features three USB ports and comes with a USB cable. Deal ends October 16.

Update: The price has increased to $19.99 before coupon, $14.99 after.