I'm going to warn you, it's not going to be cheap. It's from an X5M's accessory options, here you go:
http://www.realoem.com/bmw/showparts...33&hg=51&fg=45
You'll see there are multiple pieces for the full Piano Black interior trim. Get each part number and price it out here:
http://www.m3post.com/forums/showthr...ight=OEM+parts
For instance, the largest piece: 51459211010 it costs about $200 alone.
http://www.ecstuning.com/ES1877062/
The entire Piano Black interior will cost you around $1000 or so. If you're too lazy to get the numbers and price it out yourself, then you can call it in to the dealership, give them your credit card number, bend over, and take their pricing.