Even before I ordered my Z4 I didn't like the standard selector knob and tried to find a solution to put the DCT-knob on the Steptronic. I wanted it to look exactly like the DCT (the complete set with the cover, not just the knob itself), honestly I don't like the result shown above. There are actually some models (5-series and 6-series) the have the same Steptronic as in the Z4 but in combination with the DCT-knob. It could/should work but I didn't find anybody to do the transformation at the time.
Than, a while ago, I saw the one from the Performance serie but they were only available for the 3-series and the 1-series, but you can order the whole set (knob and cover) or only the knob itself. Asked my dealer if he could order it for me to try it on my Z4 and if it didn't work that he would take it back.
It worked and it really looks great... I am very pleased with it.
This is the one I have...(that's not a picture of my car, I believe it's actually a 1-series)
Grtzzzz