For the steering wheel, go to ebay. I know I've seen several in dark neutral color on there recently (I've been looking for a 2000-2001 Eldo wooden wheel in neutral shale to fit my 95 Deville, no luck). I've also seen a couple in black.
For the shifter, try one of the Cadillac salvage yards. Don't seem to pop up very often on ebay from what I've seen.
KDirk