Waiting for my GL-MT300A to arrive, what portable battery pack should I get?

I just ordered a GL-MT300a. My goal is to use it primarily as a small, portable NAT so I can access my media with my various phones and wireless devices that don’t have expandable storage of their own. As such, I am probably going to be leaving it plugged in to a portable battery pack morr often than not. Does anyone have any suggestions on which battery pack would go best in that scenario? I’d like to keep it under $50.

Any 5V USB battery will work. Choose a format that best fits your needs.

I have an MT300A and use it on the road all the time.

Personally I would suggest this battery pack off amazon, its what I use and personally I have yet to see the MT300A drain it. The router does take very little power and I bet you could probably get close to 2 days runtime off this: