I would think that any filtration system that kept sand and dirt out would have pores so small as to inhibit the flow of air, and I'm sure you want good air flow. Using a good non-pleated paper filter will most likely eliminate a lot of what you are wanting to keep out. Cut it to fit your screens and velcro it in place. you may need to do several windows to get the desired amout of fresh air. Pull the filters off when you are not opening windows.
That's my best suggestion.
Tony & Ruth........... FMCA#F416727
Newmar Dutch Star 4320, Spartan MM Chassis, Cat C9, Jeep Grand Cherokee,with Hemi, hooked up with a Blue Ox Aventa LX, and Brake Buddy.