Centre caps for 18" RS6 Replicas - What size?

[technics100]

I just bought a set of 18" RS6 replicas with tyres, they came with VW centre caps. I bought a set of stick on Audi badges to cover the VW logo, but I would like some of the domed grey Audi ones that you get on the original RS6's. Can anyone measure the centre cap Diameter for me either on there reps or originals. I found these on ebay but the seller doesn't list the size, just says that they fit original wheels and lists the part number.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=310165852758&ssPageName=STRK:MEWAX:IT

Cheers

Or does anyone else know where to get them, mine are about 60mm in diameter.