Get this one... 12000mah, and fast charging for $35
Tronsmart Presto 12000mAh USB Type-C External Battery Power Bank with Quick Charge 3.0 Technology,Total 6A Output for Galaxy S7/S6/Edge/Plus, iPhone, Nexus 6P/5X and more, Black https://www.amazon.com/dp/B01GVBFBBO/ref=cm_sw_r_other_apa_eT6Ixb1EVE65R
Here's a nice review:
http://forum.xda-developers.com/showthread.php?p=67526475