Those are the standard 19" wheels, model 345. The 5-star 20" inch wheels you are referring to are an option. Take a look at getBMWparts.com, they have the best prices on OEM parts that I've found.
Current: 2013 Monte Carlo Blue F10 M5 (ED on 9/1/12), 2014 Anvil Willys Wheeler Jeep Wrangler (weekend toy)
Previous: 2009 Carbon Black E60 M5, 2006 Silverstone II E60 M5, 2003 Sterling Grey E39 M5, 2000 Anthracite E39 540i6, 1998 Jeep Grand Cherokee 5.9 Limited, 1990 Eagle Talon TSi AWD, 1978 Mazda RX-7