The ash trays assemblies are sold, by BMW, separately from the door panel.
- Left rear door ashtray, Qty 1, Part Number 51427398885
- Right rear door ashtray, QTY 1, Part Number 51427398886
About $79 each from BMW parts counter.
It's held in with the following hardware:
- Fillister head screw, 4X12mm, Qty 6, Part Number 07147122390
Or you can go to eBay for $14 units...
You might want to find another BMW Stealership.