If your car is a manual you can buy a tiptronic steering wheel and wire the tiptronic controls the run the stereo. It takes some work, but can be done.
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2004 550 SE #1081 of 1953 (sold)
1997 911 Targa (sold)
The key is the "clock spring" which rides behind the wheel. It needs to have the proper # of electrical leads to and from it. It's purposes is to allow the wheel and it's wiring to turn without twisting up the wiring coming from the steering column.
Getting a Tip. set up sounds like a good Idea. Otherwise if your handy you could ,od your wheel with switches and just find a clock-spring.