Boat outfitters, Quality Marine, Wholesale marine.
Any of those might. Please report back when you find it!
Good luck with the search
Bored, stared at a bunch of google photos.
Put several search words like barrel bolt cleats , cylinder cleats, eventually double post cleat worked. They have two sizes 8” and 10” and a few colors.
Glad to have helped. Love a good puzzle.
Todd