Woot offers (1, 2 or 3-Pack) mophie Powerstation 12W Power Delivery Fast Charging 4,000Mah Powerbank w/built-in USB-C Cable for $9.99 (reg $59.95). Free shipping for Prime Members.

Product Description:
Keep your USB-C devices charged and ready to go with the mophie powerstation plus mini 4000mAh Portable Battery Charger for USB-C Devices. This device is a compact, portable battery pack and charger that delivers 12W of fast-charging power to your USB-C equipped devices.
The powerstation plus mini also features a built-in USB-C cable to both enhance the battery pack's slim design, as well as ensure that you'll never have to hunt for, or lose, your cable ever again. LED power indicators and Priority+ Charging give you essential battery information, and pass-through charging convenience.

• Rechargeable 4,000Mah universal battery
• Built-in USB-C cable
• Charge a variety of USB-C devices using the convenient and discrete,
  built-in USB-C cable
• 12W Fast-charging output to charge smartphones or tablets via USB-C
• Slim and Compact, easy-to-carry design
• Priority+ charging: pass-through charging sends power to your connected
  device first and then recharges the PowerStation battery.
• Press the power indicator button to check the charging status and battery level.