I presume the spinny air vent fan is made of plastic, and if so, you'll more than likely be able to pick one up from a large DIY store, according to the size of course.

This type of thing is quite popular when gas appliances have been fitted, and a need for continuous fresh arises. they were fitted in the windows of houses.

Some come with a cord fitted to open and close the ventilation. I think they come in 4" and 6" diameter sizes.