I looked and didn't see anything specifically for a combination m/w+hood.
Could check to see if there's a Heng's that would match your dimensions if you really need a damper. The dampers have been known to fall off, by the way.
Really good idea with the screens. There are pre-made ones to fit most fridge and furnace louvers. No doubt you could make better ones yourself.
Mud daubers, spiders and stink bugs can be problematic around propane appliances and air conditioners.
You might notice our signature picture shows that the ViewFinder's fridge vent covers were installed upside-down after putting in the bug screens. (Doing so is not recommended :) )