There are always some on eBay, but in a variety of conditions, some including tires, some not, very different pricing.
If you want new...well..you could go to the BMW dealership and pay $$$ to get brand new genuine BMW rims with brand new tires too. That's obviously the most desirable option price independent. Bavarian Autosport (
www.bavauto.com) carries not only replacement OEM rims, but also carries tasteful, aggressive styles from AC Schnitzer, Mutech, etc., plus they do offer wheel and tire packages. Lastly, for all other aftermarket wheels, definitely visit
www.tirerack.com. There you can order wheel and tire packages and even see the wheels on a likeness of your car before you purchase. I've ordered two sets of tires from them and they are knowledgeable, efficient and very affordable. Good to remember the next time you need new tires, at the very least.