I just bought some closed cell neoprene 1/4 -.250 thick and some 3m Scotch weld #1357 and used a stock seat pan for under 200.00 . You will need to use some of the stock seat foam for fill on seat pan .
I already contacted him earlier today about the part number on the seat, and he replied "Hi it came out of a ducati 749R kit of ducati cup.I will post more photos.Underneath is normal monoposto seat and over is neoprene RS version."
AFAIK the 749R kit never included a seat like that, and the RS cover thing is just false. So most likely it's a DIY neoprene seat.
I have the Ducati Performance neoprene seat on my bike. It is number 96959203B. However, it is a normal plastic plate with very little polster and than covered with neoprene. I think you can send your own OEM seat to a (race) shop that can cover it with neoprene.