We got front door window screens that attach by magnets, available for many vehicle window shapes, from Skeeter Beaters. (Google for web site.) Very satisfied with them. Someone who sews could probably make them easily, but they weren't all that pricey.
Some folks have posted pics on this forum of what they've made. You might try a search.
We inherited a screen for the sliding door when we bought our van used. Attaches by Velcro and overlaps. We leave it up all the time. No brand name tag, so I don't know who made it.
