Sorry to revive this older thread.
Retrofit kit is easy to get. Have your dealer installed it for you, and mention he shouldn't bother with the new shifter fascia or drilling a hole in it. The button is not a button, but an indicator. Just keep it hidden somewhere under the dash. The actual deactivation place is on the side of the dashboard, accessible when the passenger door is opened.
I got it on my Z4, and don't regret it.