You know, I never even thought of this until now. That would actually be a pretty ingenious idea.
I can't find anything on the googles, but I bet it wouldn't be too hard at all to fabricate some sort of mount using the backbone of an old Romy bayonet or something.
Cut the knife part away. Grind off most of the handle, leaving only the "backstrap" along with the rear of the handle and part of the handguard that goes over the muzzle. Then drill and tap a picatinny rail on there or maybe a little tack welding of a metal bodied flashlight right onto it.