The way I did my Fantastic fan was to install it in the bathroom in place of the cheap ineffective fan there. When I want air in the bedroom I open the roof vent and run the bath fan in exhaust mode. That brings in cool air where I want it. The same can be done anywhere else you want to bring in outside air.
As for a DC transformer yes they exist in a manner of speaking. You have them all over your house for ipods printers and many do have 12 dc outputs. Go to your local Salvation Army store as they usually have a rack full of these devices cheap. Look for a 12 DC with the amp rating you would need.
