Will this thread help? If it is the little holster shaped leather wallet that holds the key until you want it to swivel out, then it is about $6.00 at my dealer.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E