de luxe navigator rear carrier?

looking at the top of the metal dustbin which is the rear of my navigator deluxe, there are four blanked off holes in a position that may be associated with a rear carrier of some description being attached, was there one available? looking at it im tempted to make up a carrier with four studs, but theres no point reinventing the wheel if there was one already in existence? so were these four holes for a carrier or something else?

I have seen a picture of a Jubilee Deluxe with what looks like a carrier fitted just as you describe. Its has a hoop at the front as a kind if pillion grab rail.

had a look through google images and found a picture of the rear carrier on a jubilee, looks the sort of thing, will have to keep my eyes open now to see if there are any about,