I saw 2 pieces that size for sale once, and bought them, they were backers from a veneer company from the 50's. I've never seen any for sale before or since. So he'll probably have to use veneer.
I have about a dozen pieces of Honduran that are up to 14" wide, I also found those from veneer companies. So he could try calling some of them, but I wouldn't hold out much hope.