Just purchased an Audi RS6 keyring. This is my first RS6 accessory.
You can purchase it from Clair Parts
That's the only thing I can find for now.
The silver ring itself is almost 2 inches in diameter.
The leather piece that holds the RS6 logo is about 2 1/2 inches long, including the logo.
The logo is about 1 inch across, and diagonal.