I did this with my door in may before a trip down to FW. I found a local glass shop that also wholesaled lexan. yes go w/ lexan think cost was under $100 for 4x8 with cuts. Then took jig saw and back cut the edges to fit.
I sold rest for full cost- this was a was deal- advertised lexan for hunting blind.... on craigslist!!!
I put two pieces - top and bottom, then also cut 1"-2" finger holes in top of each pc so I could pull out if need be. I also used vecro to secure on lips around screen.
I am not to worried about the air flow as much as my 50 lbs lab going through the door for a squirrel or an armodillo. problem solved and my wife loves the light and that we can see our kids out front.