Probably there is no tool for this specific task, however you could look into automating it yourself in Microsoft Word by using a macro. Try searching Google for similar macros to get started.
To future proof what are you doing just in-case you need to do the same thing down the line again, do not include the content directly into the header, but instead add it as linked content to an external document. This way if you want to change all of the headers again you only need to modify that one external document in order for the changes to appear in all of the rest.