I don’t have specific examples as I have not tried to do this nor asked by anybody yet but here’s my methodology and thinking on it:
The first major hurdle in such a working is the obvious elephant in the room: the past that you and this ex shared. And obviously if broken up there is some history that will remind this person of why they are not with you anymore.
So one of the ritual would likely be devoted to working on those memories of this ex and either softening them or, with more difficulty, having him/her forget the bad stuff. Hopefully that’s the only thing that broke you two up in the first place.
The next thing that would likely be a major hurdle is just general incompatibility. And for that I’m afraid there’s no simple ritual that fix that; at best a spell will bring you two back together but any underlying incompatibility issues will eventually creep back in and break you two up again. But at least you can have a second chance.