Yo, I just discovered that literotica has a cuckquean tag.
You must be registered to see the links
Some of them are kind of meh, some of them are mistagged, but some of them are straight up literary masterpieces, highly recommenced it you're looking for cuckquean stuffs.
Also, there are stories on there that are tagged cuckquean, but don't have a shred of relevant content in them. So, it's also a good idea to just search it as a key word (you go to "explore" at the top of the screen, and then you go to "search)"
and also, you can pair it with other tags and categories on there
But I have to warn you, some folks on there a super toxic for some reason. I wouldn't even touch the forums on that site.