Wanted - 4 bolt towball

[NickBab]

I've recently purchased a 72 bay with a towbar buried behind the bumper, but with no towball. It has 4 holes through the bumper into the tow bar to mount the ball / hitch. Does anyone have a tow ball or know where I can get one to fit?

I can't find any make or model on the towbar itself.

Thanks
Nick