Falling tree limb in a rain storm bashed chunks out of mine.
Time to get up on the roof with a ladder. These shower skylights seem to be standard sizes and I just replaced the one in my Roo -- drastic different "RV" from yours.
My cover is 17"x25" which appears to be a standard size to cover the 14"x22" opening in the ceiling allowing room for caulking. This is a very common size. I bought a completely clear cover along with an inner cover with a clear top section. Clear rather than translucent? Will no doubt be translucent in a couple of seasons. As of now the extra light is nice.
I found mine just Googling the outer dimensions. Hardest part is getting all the old caulking off. I put a step stool in the shower and stood chest high the opening to remove the caulking. Had to go back on the roof, of course to screw and caulk the new cover.
Perhaps not your size but here are mine.
Skylight:
https://www.amazon.com/SCT-Skylight-...dp/B09SBQMJVR/
Inner cover:
https://www.amazon.com/gp/product/B09SBQC757/
-- Chuck