Mitsubishi W003T19571 - BMW 7172536-7172536. Mitsubishi W003T20071 - BMW 7237647-7237647. Mitsubishi W003T23171 - BMW 7318327-7318327. This is for a replica ballast (details below). Xenon Ballast. If you have tried changing the bulb and it is still not illuminating then chances are you have had a ballast fail.
eBay