You should be able to buy steering wheel buttons
by: Mike Ernst on 2003-01-03 at 21:28:16

I have the older style steering wheel (four spoke) and I had to replace my buttons to make the SES Voice Module work in my 98. I ordered just the button assemblies and replaced them myself.

Here is a picture showing separate part numbers for the steering wheel buttons:

Mike Ernst
98 540i 6-spd