Excelsior Plum where to buy

I live in Glen St. Mary, Florida. Where the excelsior plum was discovered by George Taber. My grandpa talks about yellow plums that he ate when he was a kid and I’m assuming it would have to be excelsior. I have been trying to find some to purchase and plant and can’t find them anywhere. Everyone is out of stock and don’t know when they would have any available. I would greatly appreciate any help in finding some trees to purchase.
Bryan H