Many states have junk yards. Alternatively, if the dimensions are the same you might find something on big sites like Etrailer.com
Always good to post the make, model and year of your RV and pictures of things you need help with. If it's glass or hard plastic an glass replacement company can cut a piece for you if you can bring in the frame.
2017 SLX 195RB
2021 Jeep Grand Cherokee Summit L 5.7L V8
Andersen WDH hitch, Renogy 100 AH Lithium &
200 Watts solar panels from Renogy
Prev. '14 Jeep Grand Cherokee Overland, gas 3.6 V6