Hello and thanks for posting further info.
I am indeed looking for both sizes, for holding the fore and butt sections horizontally, for use in a carrier or jeep as well.
I emailed this website;
http://www.ww2fabrications.com/britishairborne.htm
and they told me that they are reproducing these mounts, however they are currently out of stock, but were hoping to have some more produced in a few weeks.
I have attached two photos for examples.
Cheers,
Rob