The camera's battery has a capacity of 1800 mA Hours. The hub will generate enough energy to keep it charged. As you have already stated, the problem is that there doesn't seem to be a charger that accepts power from a USB hub. However, there are chargers that accept power from a car adapter. They often include a spare battery, so you can keep one charged while using the other. For example:
You will want to set the e-Werk to it's maximum voltage output. The power outlet from a car is typically a little over 14 volts, but 13 volts should work fine. Positive voltage goes to the center connector of the adapter, negative voltage to the outside ring.
If you want to know more about charging hubs, I wrote a post here: