Reddit mentions of Heng's 90043-CR Replacement Vortex I Fan

well, if you have a traditional vent, there is the fan insert that is about $45 on Amazon. A PWM speed controller is about $8. Comes w reverse.

will look up the parts.

as far as 'rain proof', install a vent cover.

The Fantastic series has a rain sensor model that will close the vent. About $300+

https://www.amazon.com/Hengs-90043-CR-Replacement-Vortex-Fan/dp/B002N1J5IM

https://www.amazon.com/Pixnor-Controller-Adjustable-Reversible-reversing/dp/B01H1W79S0

https://www.walmart.com/ip/Camco-40421-RV-Aero-flo-Roof-Vent-Cover-White/29764356

so, $45+8+22, or $300+

I got one of these to put in my sunroof. I will take it out while driving.
Heng's 90043-CR Replacement Vortex I Fan https://www.amazon.com/dp/B002N1J5IM/ref=cm_sw_r_other_apa_SiPvzb19T5VKR

I added Sumosprings to mine combined with a 6k wdh.
Mine has factory tow package.
Avg 10-12 mpg on hilly terrain.
Under 65 mph hwy.

Here is fan
Heng's 90043-CR Replacement Vortex I Fan https://www.amazon.com/dp/B002N1J5IM/ref=cm_sw_r_cp_apa_G8q0BbHRYQ15J
The frequently bought together link shows PWM speed control. Read fan reviews for how to.

Fridge fan was an ebay kit I found for $20ish.
12v computer fan and wiring with switch.
Mounted fan with zip ties on inside of top vent to pull hot air out.

Had room for 2nd battery alongside first on tongue. Bought battery from Costco, cables and battery box on Amazon.

Starcraft screen is a roll up style that retracts.
Keeps bugs out, more natural light and nice cross breeze.

Have considered ramp door as a potential deck, but with little ones and no railings like bigger models I passed.

Yours have roof or side A/C?
If roof, then the odd counter space above fridge makes a great place for a 3 drawer Sterlite plastic shelf. We put one up there when onsite.
Without much storage it helps for longer getaways.

Enjoy!