Last week I posted about a Anker PowerCore Slim 10000 portable charger, which can be recharged with a USB-C or Micro USB cable. I included a promo code but some people had trouble with it. Here's a similar Anker charger, the Anker PowerCore Lite 10000mAh,* which has a coupon on the Amazon product page for a great discount. Note that the power input it USB-C only.
(This link takes you to a page with a button that lets you buy the charger on Amazon.)