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: 2016 Silverstone M5, 2014 Anvil WW Jeep Wrangler
Previous: 2013 Monte Carlo Blue M5 (ED on 9/1/12), 2009 Carbon Black M5, 2006 Silverstone M5, 2003 Sterling Grey M5, 2000 Anthracite 540i6, 1998 Jeep Grand Cherokee 5.9Ltd, 1990 Eagle Talon TSi AWD, 1978 Mazda RX-7