Oil preheater in aluminum trans pan

Do like most of us do-
On a good floor jack lift the butt of the car by the center chuck and run the car at low rpm with the wheels lifted before you run.
Warms things up easily.

If not Napa sells a stick on 120vac pad made by KATZ like 150-250 watt. Pad is self stick and made to be perminate. I use them on hydraulic tanks here in New England to keep systems warm during cold temps.
You can easily run off generator. Honestly I don’t see a need for it, it’s your car and I understand wanting to go the extra especially when spending money is involved.