http://www.amazon.com/115V-AC-Cooling-172mm-150mm/dp/B005F1MX54 is 150mm in diameter and may do what you need for a fairly reasonable price. It's not quiet, but boy will it move a lot of air. If there is no speed controller/thermostat, you could use a wall dimmer to slow this down a bit and reduce the noise a lot.
no subject