Couldn't you rig the dials up separately to a 9v battery? Are you going to make some kind of cockpit with a dashboard then? It'd look cool with lit up dials, but as the above posts have said, it's not really possible to use the DFGT's power supply to light them up without a serious amount of modding to the power brick.
This was what I was thinking, but would 9V be enough to power the gauge?