Welcome aboard 01Maxum2300SE!!
You won't find an item like that in stock. I doubt you'd find one from a parts boat. I would either work with a local fiberglass fabricator or ignore it. You could remove the ladder, fill the holes with epoxy and leave the ladder cover as is.
I'd print a small sign and affix it to the inside that reads "What are you looking in here for??" But that's my odd sense of humor.