Want to add power vent in opening, need a hot wire

[mikee409]

We have a Vista 27-PE. the 2nd vent in the roof did not come with a power vent only the bathroom has a fan.
I found an insert assy to add a fan in the existing opening. There are no power lines near the opening that I can find. I removed the vent assy hoping there was a unused 12volt line in the roof space but no luck.

Does anyone know where I can pick up a 12 volt feed near this location.
I was thinking I could jump from the bathroom fan power line across the roof and pass it into the 2nd vent.
I really don't want a wire running outside across the roof. Install has to look good and not shade tree mechanic looking.
Mikee