The real thing aren't that expensive; I sold mine to Speedinfusion pretty cheaply. If you want them brand new, tirerack.com has them, not branded for BMW but still made by BBS. If you don't mind a scuff here or there, try ebay; they've always got them.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.