I paid about $54 (2000 E150) for front windows from Skeeter Beaters.
When I thought they were MIA I sewed a panel (second picture attached with black binding tape). 7-8 magnets makes a very secure connection, though I hear mosquitos in alaska are ferocious so may need more up there
The Skeeter Beater design has 20 ceramic magnets. You'd think more would be better but they are very cumbersome to install as the magnets attach to themselves and its tough to get it laid out.
I am about to leave on a trip (Baja) so don't have time, but I will probably sew a new set with 1" Sunbrella trim around the edge to proved a little structure. The binding tape I used is a little lightweight. Also, the screen material I purchased from Amazon is very stretchy and fine mesh. It's difficult to cut and work with. I'll find some decent quality screen used in tents.
I also purchased a screen for the side door. Skeeter Beater is a solid piece also with a gazillion magnets. It's frustrating to install and has no door so best bet is entry via the front passenger side door. I think it was around $110 from Skeeter Beater. Not a bad price considering all the magnets, but not a great design.
For the side and back door openings, I really think snaps are the way to go. A 2" Sunbrella "frame" with snaps, and a verticle split door with magnets. This way, the screen is mounted inside and the doors could be closed while screen is in place. Would not be the cheapest fabrication, but would be the best in my opinion.
Peter