Not a recommendation, but you should look for a big fan, not a small one. The bigger ones are a lot quieter, as they don't need to spin up as fast to push the same amount of air. The tiny fans sound like jet engines, please don't get one of those!
Alternatively, you could go with a fan that you flap with your hands, they usually fold up neatly and you don't need to go looking for a USB outlet. Perhaps not as convenient though