Why not towable gas generator trailers that you can rent for long trips.
Hook it on, plug the connector up and attach your license plate to the back (or use eink).
Years ago I saw some one who had sawed off the back end of a late 1980s Chevy cavalier (or similar) and turned it into a portable generator trailer for his EV. This was so long ago it was probably an EV conversion of some kind.
Alternatively, put a battery in that trailer. See for example https://far-a-day.com/en: “Like an external phone battery, but for your car!”