Why not just a 20" x 40" recessed insert? Cheaper and always there when needed.
You could even make it removable and have a piece of hardwood insert for regular use and swap it when the need arises.
My son gave me two sold wood executive office doors that are 40" wide x 9' feet long and
1 3/4" thick.
I haven't decided on the finish yet. I'll be watching here for more suggestions to the OP's request. Even if the thread was dredged.