To me, the answer is simple and totally obvious. Replicate a "school gun". The 23" barrel is like nothing else - cut it to 22" with a proper crown, and reduce the area ahead of the front sight base to take a standard bayonet. You have harmed nothing but will end up with something believable. Stock work should not be difficult, though you might have to plug the lightening groove - but that would be "correct" for that length barrel. Totally "win-win".