Emergency charge using portable generator

Some guys on youtube did that. They took a Lightning and a Hybrid up to Alaska on a multi-day thousand mile trip and the recharged the Lightning every night with the Hybrid. Worked for them, so it's not out of the question.

I think the questions is, can you travel with a generator in the bed of the Lightning and charge yourself up (albeit for many hours at a time, maybe while you sleep in the cab) and get enough range for next day?
Is there a portable generator that wouldn't take up the whole bed and need a forklift to move it that would do the job?

Curious minds want to know.

True that!