I know anker gets a lot of positive action here but I bought this 9 months ago and have used it a few times a week for long durations and works awesome and the price can't be beat! EasyAcc 20000mAh Power Bank (4A Dual-Input, 4.8A Smart Output) https://www.amazon.com/dp/B01422TC14/ref=cm_sw_r_cp_api_YgV0zbD4QPJJ8

That's why I bought one of External Battery Pack My battery life was already really suspect, so it's an amazing purchase for this game and just a really good purchase in general. And I got it with 1day shipping on Prime.