So I don't have access to the bag. The website doesn't seem to offer measurements on the battery pack pouch and I can't seem to find a picture of it with any valuable scale. Are you able to provide some measurements to the space or size of the largest thing you can fit in there maybe?

I have an Anker Powercore 10000 and an Anker Powercore 5000 and both are pretty darn small so I would hope they would fit. Depending on device the 10k mAh can charge your phone roughly three times and the 5K One and a half times before needing a recharge. I find the 10K small enough that I use it as a primary charger and keep the 5K as an extra backup when I really want to go lighter.