I'm not sure where to get that, but you can get a plastic insert that was used in 92-93 before the trunk lid change, which fills the space and looks very good.
I always thought the reflector ones looked kinda tacky.
But the body color insert looks very good, changes the look of the whole rear of the car in my opinion.
Add on 94-95 taillights, and you are set.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.