Hi,
I just bought an OEM Alpina front spoiler for my Sterling Grey 3.0i. Havent got it fitted yet but will post pics as soon as I have.
Although, plenty of pics of Z4's with Alpina fron splitters on google.
http://images.google.co.uk/images?hl=en&q=z4%20alpina&um=1&ie=UTF-8&sa=N&tab=wi