I feel a bit silly posting this, but on the logic that, if it works, it's not stupid, I think it is probably OK.
It is far too hot for me at the moment, and I have better things to spend my money on than a properly designed fan. So I got an old pc case fan, stripped the wires, wrapped the black round the outer conductor of a random 12v wallwart plug, taped it up, then stripped the red, poked it inside, and taped it. Stuck the fan on my desk with blue tack.
It is awesome. I spent nothing, and I am no longer soaked with sweat.