The Bentley Brooklands, Azure, and Arnage centre cap 20" is a genuine manufacturer part number 3Z0601161A that is designed specifically for Bentley’s. This centre cap is a high-quality plastic and needs to be painted.
The center caps are no longer available, but I have recreated them, and they fit perfectly. The picture shows one fitted onto the wheel. 
THE PRICE IS JUST FOR THE CENTER CAP