I was looking to add a fan to the roof vent over the bed without spending alot of money. The fan used in the bathroom works good but a fan like that is too Loud for over the bed.
I came up with another solution I installed a Computer Fan "120mm 12cm PC Computer Clear Case Quad 4 LED Light CPU Cooling", they are $4 with free shipping on Ebay, I also had to buy a switch which was another $3. They come in clear with LED lights inside, I have purple light, which is not that bright.
They use very little electric, lightweight, and are super quiet, the holes line up with the holes in the vent frame (you must provide your own screws). My wires were under the cover.
They are nowhere near as powerful as the Bathroom fan in the amount of air that is moved.
Ideally the best Fan for over the bed would be The Fantastic and Maxxfan.
We usually will sleep with the AC on if it is 70 degrees or warmer, so the fan is good enough when we don't use AC on Cooler nights.