Pretty specific part but you can try
https://www.greatlakesskipper.com/ If it's a fiberglass part made by Four Winns you will probably not find it but keep trying, you never know.
I saw your other similar post. If it's a good fiberglass person they should be able to match the color, even faded, but it will never look like the one you had with the exact same fading.
I am not sure what the part looks like, is a very visible? Maybe you can cover it with something else, like vinyl that matches your seats. Can you recreate it with starboard or is it fiberglass molding? Any pictures on the boat?