Todd,
I had to replace mine also, it is not hard or expensive. Below are some pictures of what I used which is a reinforced 3/32 baffle material for airplanes.
The top picture is the top of the radiator area. In your pictures, you can where your top baffle has come loose and is laying in the engine bay wrapped around the hydraulic cooler hose!
This is the original lower baffle piece in my coach, same as yours, it broke loose but in my case is still partially there.
Another angle of the lower piece that you are missing. Again, just rubber sheet pop riveted in. Just note, when installing new your objective is to isolate the radiator from pulling air in from inside the engine bay. Also, don't drill into the radiator core if drilling new holes in the shroud for rivets or screws. There is plenty of room, it is not hard to avoid miss drilling but just know you need to check before drilling...
The material I personally used. It is fiber reinforced so it will last longer and better than the pure rubber sheet Monaco used. It is very similar to this item however I used 3/32 instead of 1/8th:
https://www.aircraftspruce.com/catal...own8071-36.php
I think you would only need a section maybe 12 inches by 36 inches or so to do the rear of the radiator. A roofing company may have rubber sheet you can use for much cheaper. McMaster-carr also as chargerman pointed out but the pricing is not great there IMO.
Windecker