And an 80 lb battery to power it. Or maybe a couple of solar panels.
Clip-on solar fans are $5.
Actually, the big PC cooling fans and a small battery would be a pretty good answer. They’re quite efficient.
And looking for one of those, I found this battery power stroller fan.
https://www.amazon.com/VASG-Operated-Stroller-Portable-Rotatable/dp/B08XQFFS1L
I’d want one that used DeWalt battery packs, since I’m in their battery tool ecosystem and a have a bunch of the batteries.