There are quite a few out there. In some fanfictions, Bill's werewolf nature adds a layer of danger and mystery to his relationship with his mate. They might face discrimination from other wizards, and the story could focus on how they overcome this while also dealing with the monthly transformations. For example, in 'The Werewolf's Love', it shows how his mate stands by him through it all.
Well, I'm not sure of a specific one off the top of my head, but generally in such fanfictions, the relationship between Bill and his mate is often portrayed as very strong. The werewolf aspect might change how they interact with the wizarding community around them. Some stories might also explore how Bill's family, like the Weasleys, react to his new situation and his relationship with his mate. It could be a story full of love, sacrifice, and the struggle to fit into a world that can be unforgiving towards werewolves.
One popular 'Harry Potter' fanfiction with this theme might be 'Moonlit Bonds'. It delves into the relationship between Bill, as a werewolf, and his mate. The story often shows how they navigate the challenges in the wizarding world with Bill's condition.