Where are you located? I think it’s a local market thing. In the US and Australia the standard hitch is a “receiver hitch” with a two inch square socket. In Europe I believe the standard hitch includes the ball.

 

I am sorry I do not know the part number. Surprised that Land Rover USA's website wouldn't possibly have a way to obtain that? Mine was installed at the dealership. Here in US, it's a standard type of hitch for this vehicle. it also allows electrical connection for towing a trailer.