Hello Mike,
Yes, even if this is slightly off-topic, there are Mercedes 15" hubcaps around. Those were (are) used on the fireworks- and ambulance versions of the W 115 sedan and also on the W 100 (MB 600, Grand Mercedes, 1964-1981), at least during the later production years.
They're still factory-available, but I believe they're pricey now.
The original 14" (6J x 14 H) Mercedes bundcake aluminum rims have a 109 parts number; I believe 109 400 09 02 but I am not absolutely sure.
Greetings,
Achim
(Magdeburg, Germany)