I searched on Cragislist and Ebay for any sets of original Headlights coming off a 2000 to 2003 E53s with Xenons. You'll have luck with any 8cyl model from that time frame. The ones I found had bulbs and ballasts, however I did order new bulbs just so they wear out evenly.

The set up for the install is slightly different than just plug and play being the halogens don't have a bottom plastic bracket on the housings to hold the ballasts.

I had to zip tie the ballasts because again the brackets from the xenon headlights don't fit into the halogen set up.

If you want to be 100% sure about part numbers, I use this website as reference all the time: BMW Parts Catalog