I have two and can heartily recommend both. Both are 12v.
The
Sirocco II fan: light-weight but durable, super quiet, 3 speed, direct wiring, great purchase. Do a search for it in the boat world and you'll find rave reviews. I may get another and keep one on a portable mount for the rooftop tent, then just leave it up there when it's closed.
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I also have and love the
Fan-Tastic Vent Endless Breeze fan: a good bit larger at 14.5" x 15.25" (approx 37cm x 39cm), is more of a box fan; quiet but not as much as the Scirocco II, also rave reviews from most, and has a 12v plug instead of direct wired. More portable than the Scirocco in that it has pivoting feet, too.
Mine was $75.05 USD when I got it almost 3yrs ago, and I see they've gone up a good bit, like so much other outdoor/recreational gear lately.
I don't have a photo of mine, as it's buried in a tote while using my van for hauling storage stuff, but they look like this:
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Lastly, while not 12v but uses the 18v battery packs from cordless Ryobi tools, this little portable fan has saved my butt more than once when hauling expedited cargo around North America. I still use it from time to time under the awning when in the swamps or desert and need some air moving. I keep several inexpensive cordless Ryobi tools with me when adventuring like an impact driver, drill, etc, so it's a gimme to throw this in somewhere, too.
Ryobi Hybrid 18v: pivots, will hang, and is nice because you can run it on AC, too, so can plug it in if you have shore power.
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