Hello and welcome to Bimmerfest.
Unfortunately You've posted in the e89 Z4 (2009-current) sub-forum. I doubt anyone with a 2003 Z4 will be here to read your question.
BMW sells the entire unit. What you can get from salvage yard is up to them. Normally they would sell the entire unit as well.
The models and equipment (standard and optional) illustrated in this post reflect my misunderstanding of vehicles supplied by BMW AG to the German market. In other EU member states, the truthyness of my posts may vary. Please ignore this post. Subject to change.
Last edited by Andrew*Debbie; 02-12-2012 at 12:10 AM.