One option: http://www.gadgetjq.com/lj_windshield_vent.htm
beat me to it! I was going to suggest a GW vent.
I have both models of Cee Bailey windshields-- I use the taller one for longer trips, and am thinking of installing a GW vent in it...
If I screw it up, it's OK because I can use the smaller one just as easily.