You might have to look around and you might have to make some phone calls and emails rather than just searching on websites.
The reason for this is quite simple. The three point star is a protected logo of Mercedes-Benz and believe me there is no more logo from any company anywhere on earth that is more protected. Any reproduction hubcap is basically illegal. When they find them, they shut it down very quickly. Nobody wants to go up against the Mercedes-Benz lawyers. Their pockets are very deep and their patience is very long.
That being said there were plenty of them made by different manufacturers. So there are going to be some available out the back door and through eBay.
None of them are nearly as nice as the ones from Mercedes-Benz.