I had Camping World replace the pop up vent with a Fantastic Fan. They could not find an always hot lead. They said they would have to pull down the cabinet where the switch for the lights is. I had them tap the ceiling light, which means the lights need to be on. I just turn them off when not needed so the fan can run, and the rain sensor will work. Eventually, I'm going to see if I can use the existing hot feed to pull two wires through from the light. I'll tie one to the hot side of the switch to feed the fan, and the other will replace the light wire that was uses as the pull. Not sure I'll be able to do this, but worth a try.
2013 V 3105
2016 F350 King Ranch CC 6.7 diesel dually