Help with phone

Just bought an '02 C320 sport with command & nav. It originally had a phone, but that has been removed, along with the cradle in the top of the
What exactly do I need for this model year C class? I see the phones all over ebay, but none seem to have the cradles. Is there even more than the cradle that I will need to make the system operable? Are all of the phone "guts" in the cradle which plugs into the socket in the console, or is there a larger "brain" that goes somewhere else in the car?
The messages on the dash and Nav display simply state "no phone connected," so it seems that the system is ready for one to be plugged in.
Thanks! DS
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