BMW has created an organization within the company specifically responsible for the care and service of older BMWs.  They call it “Mobile Tradition,” the group was formed in 1994 and it focuses on BMWs which are 20 or more years old, though it addresses some models which are much younger.
   
Through this group, the company maintains close contact with over 600 dedicated BMW clubs, which helps it gauge where it should focus its resources.  One of its prime purposes is parts availability.  Among its targets are the 2002 series cars and the original 5 Series.  The Z1 is also one of the cars under their care.
   
When Mobile Tradition takes over a BMW model, it takes over the parts distribution for the car.  But it also gets all of the associated tooling.  In some cases, it will reproduce tooling which has worn out in order to meet continuing demand.
   
Moreover, one of the core purposes of the program is keeping down the cost of parts for older BMWs.  The aim is to keep the parts cost at about the same level as it was when the cars were new.
   
There is a website for Mobile Tradition, but finding the parts availability part of it takes a little navigating.  So, here’s the link to parts and the parts catalog: http://www.bmw.com/com/en/insights/history/mobiletradition/popup_index.html.