I have only linked you to a discussion about what you are asking and a plugin that another site has used to build your own custom header so you can see an example of what you are looking for.
If you are looking for a plugin that is ready for use, at the moment it does not exist because it has been replaced by the theme components. Furthermore our themes don’t work only by changing Html and CSS or JS but they can also overwrite templates almost like a plugin does.
See Developer’s guide to Discourse Themes for more info.