I kept getting frustrated when i would go through water and the front windows would get fogged up from steam so I worked up this defogger system.  This is good for one side only.  This is small enough to have one for the driver and one for the passenger.

I used 12V 50mm fans from Amazon.  Look for the highest amperage and CFM for the best results.

These worked OK:  WINSINN 50mm DC 12V 5020 Dual Ball Bearing Brushless Cooling Fan