In one of my previous campers I tapped into some of the 12v lines that ran nearby. I used a voltmeter and a pin to test. You might find you have some wiring near by. Grand Design might be able to help you in your quest.
As for a fan, one of the best things I ever purchased years ago was a
Fantastic Vent Endless Breeze 12v fan. No need for an inverter and it's very low on consuming power.
How big of TV are you talking? Some of the smaller ones can be operated off of 12v power.
Two Wire Fox Terriers; Sarge & Sully
2007 Winnebago Sightseer 35J
2020 Jeep Gladiator Rubicon