The reason i ask why is to try to more completely understand what is broken or damaged and what is not. If the binder bolt barrel is damaged it might be able to be replaced/repaired without dealing with the rest of the lug. If the lug is cracked then there's a real chance the underlying tube is also. So the "why" is not to question your motives but to try to guide you better. I called this question "loaded" because of the answer will have a lot of bearing as to what cost or possibilities might exist.

So to back up. Why do you ask this? Is the lug cracked? The binder stretched so it bottoms out without holding the post? Is there a nonstructual reason? Are you concerned about the tubes' conditions or the stays' top cap style?

There are more questions that I could ask but i hope you get the idea that being one of the more complex junctions of a frame the answer (and cost) is also complex. As rellis asked, any photos would help us understand the construction style as well as a possible crack/failure reason. Sometimes fixing the problem is more involved then replacing the broken part. If i wanted to flame you it would have been far more aggressive than my reply was. Andy.