I have an older model two horse stock-type trailer with the slats on the side. I have plex-glass in the slats, but for the warmer months would like to add screens to slide into the slats. Would anyone happen to know someone who makes them?
There are local shops that make made to order, off size screens for builders and remodelers.
They made a parlor door screen (those double doors to the yard where only one opens) with a dog door on the bottom for us, our builder ordered it.
Check in your area who makes those and ask them if they would make some for your trailer?
Home Depot/Lowes may know who makes those where you are.
We used the local screen shop (small independent business) to put solar screens on a combo stock trailer. Made a noticeable difference in how cool the inside was during summer.
Covers and All will make custom screens for CHEAP. I had 3 made for the windows on my trailer and the total was less than $50.
You can make your own. I camp in my trailer. I bought screening at Lowes, cut it to size and added magnets so they snap on. You can also use Velcro. I’ve seen that done as well but the velcro had to be glued to the trailer as well.
It sounds like you are wanting something more permanent though.