They are an official Morgan factory spare part, but don't have the part number. They come in black or brown. I noticed them on an early CX Plus Four in the showroom at Krazy Horse, when I took my car to be serviced. So they ordered them in for me.
They are an oblong of thick saddle leather complete with a smaller metal reinforcement rivetted onto the underside of the leather, which also acts as the attachment bracket. You undo the seatbelt guides attached to the top of the seat back and pop the new parts between the guides and seat back and screw both back on to the seat. Took me 5 minutes.
I tried to post a photo, but it has defeated me. You can see them here:
https://www.torque.com.sg/news/all-new-morgan-plus-four-unveiled/Martin
