Bestbuy offers myCharge - AMP PRONG 5,000mAh Everything Built-In Portable Charge for Most USB Enables Devices - Gray for $18.99 (orig. $39.99). Free shipping for Members.

Product Description:
Keep your mobile devices powered on the go with the myCharge AMP PRONG 5K portable power pack. The 5000mAh capacity powers up to two devices simultaneously. The myCharge AMP PRONG 5K portable power pack has USB-C port and a built-in USB-C cable that deliver up to 12W of output for rapid charging. The device has built-in wall prongs for rapid recharging of the powerbank.

• Compatible with most devices with USB Type-C charging capabilities, including wide variety of smartphones, tablets and more
  You can stay connected on the go no matter what you're carrying.
• 5000mAh battery
  Lets you recharge your device so you can talk, text, and surf longer when you're out and about.
• Built in cables
  Features USB-C port and built in USB-C cable to charge up to two devices at the same time.
• Built in wall prongs
  Features built in wall prongs for rapid recharging of powerbank.
• Pass-through charging
  You can charge your phone or tablet while the power bank is recharging.