Gen 3 Prius (Audio/Electronics) :: How To Hide A Power Cable

Have a 2010 Prius V, and use a smart phone with a vent mount above the radio. So far so good, however the dangling power cord I'd like to minimize. Presently, I have a tiny cigarette lighter to usb converter located under the shifter (in that odd open bay), and then the cord travels up the entire dash.

Would like to run the cord behind the dash and, if possible, have the cord pop through the air vent to power the phone. That said, would not want to interrupt air systems by puncturing through the duct and am not familiar w/the schematics to understand what options exist under the dash. Prefer not to drill through the dash, but would consider. Second, but lower priority, would be to hardwire the cable inside the dash.

Best spot I can locate as an exit for the power cable might be the space just outside the air vent, but still inside the vent cavity. have links to the dashboard schematics to get an idea of available space?