Many have tried it and many have failed, some say they succeeded. Maybe you call the companies like BMA, or similar, as they do not have the parts available online. Maximilian is apparently also a source. In Europe you cannot buy these parts for safety reasons, just a remade one from BMW.
Autohaus is apparently the cheapest one for complete new ones
http://www.autohausaz.com/search/pro...ter%20Cylinder
Or try here and call Patrick
http://catalog.bmaparts.com/epcvsoap...entid=bmaparts
Complete list of oline vendors
http://home.earthlink.net/~hainesinutah/bmwvendors/