Originally Posted by Bald Paul

Here you go:

PowerCore 5000 - Anker

A Garmin 1/4 turn mount with bands fits perfectly around it. You can either use another Garmin 1/4 turn banded mount with two phone case adapters stuck back to back, or Shapeways makes a banded Garmin mount, with male fitting.
Here it is mounted, with the GoPro camera, Flare RT tail light, and Varia.