On the bimmer.org M5 board a while back, someone mentioned an add-on cupholder for the 5-series, but didn't give a part number. I went to a BMW dealer, and all they could show me was something designed to fit an E34. However, when we looked further in the online parts catalog, we saw a piece on the exploded drawings for the E39 interior console which looks like a removable stabilizing sleeve insert for the standard E39 cupholder. It's labeled '18' in the drawings, but no matter what model of car we selected (528, 540, M5; American, European, Japanese, or Russian) the system popped back with "This part is not installed on the vehicle specified" and wouldn't give us a part number.
Does anyone know what this part is called and how to get a part number for it?