It's the 'brad' type button correct? The one that's completely metal and stamped on, not sewn with thread? You can buy replacements here in some larger fabric stores. Perhaps you could find those. It won't say Levi on it, but no one should notice :-) You might also try removing that button from an older pair of jeans carefully and see if it can be used in it's place.
Login using the form on the top of the page to post feedback (if you are a registered user). If you have not yet registered, click here to do so. It's FREE!.