Mine are actually replica 20's from Eurotech Wheels - they had 21's but the tire availability was slim. I am not sure they sell them anymore due to legal issues with BMW.

I have seen some on eBay, but they were a couple grand for the wheels.

__________________
2001 X5 3.0i (PP/WP/AP) Traded at 213K miles
RARE White on Black - Why does everyone get Tan??
First E53 with 215s on XOutpost!!