[NGR]

A couple of thoughts...

People have tried using generators and an outlet charger on EVs but found the car doesn't like it because the earth isn't good enough. A metal spike driven into the ground and connected to the generator chassis apparently can work. Might as well add some gas to the fuel tank and charge while you drive.

If you try a battery pack (like you've got for a cellphone), you're carrying a lot of weight around to make any meaningful difference - a gallon of gas/petrol would be easier, and you can charge while you drive.

I doubt the car would like to charge through the charge-port when in motion, some serious software changes would be needed - and where would you put the power source (on the passenger seat and run a cable out of the window?)

Filling the fuel tank sounds like the simple option - use the on-board charger that is built-in from the factory.

On my commute, I use e-drive to get to the freeway and try to top up the battery using sport so I've got enough juice to get in and out of town on electricity.