Great idea. Bugs can make you miserable. Here's something similar to what you're looking for. It looks like the screen is in a pocket shape and just slides over the whole window frame. You could probably sew up something like that with some mosquito netting.
WARNING & DISCLAIMER:
SELECT AND USE OUTDOORS AND SURVIVAL EQUIPMENT, SUPPLIES AND TECHNIQUES AT YOUR OWN RISK. Information posted
on this forum is not reviewed for accuracy and may not be reliable, use at your own risk. Please
review the full WARNING & DISCLAIMER about information on this
site.