Morning Louise
Welcome to the Forum
There is an online parts list for all BMW cars www.realoem.com put the last 7 digits of your Vin number into the search box it will bring up your model, the open the headlight section you will have the part number you need.
There are several BMW specialist recyclers out there Google will help plus Ebay
What is the issue with your lights ? are they cloudy? if they are the lenses can be polished. Your lights should be Bi Xenon so plenty of light so is it an issue with any of the control units (so you may not need complete lights)
Dave