A google search shows some for sale over the last couple of years, but it looks like they were only limited to 50 produced. I'm guessing it would take a lot of patience and money to actually be able to buy one.
The fallacy is many if not most of these 'commerative/limited edition/special' is their premium is seldom investment grade. So there needs to be some other reason to buy, cause the financials don't hold water.
As such, I'd pay someone $100 for the name and email address of the person who bought it. I have some land to sell that Billy the Kid once rode within 300 miles of.