I also found another site for something that is apparently not widely stocked at tire stores. For anyone with custom wheels, you should be using hub-centric rings. These fill the space between the center of the hub that the stock wheel usually sits on, and the inside of the wheel center. It takes the side sheer load off the lugs and nuts and helps to center wheels onto the hub. Without them, you could get a bounce in a wheel, or even break your lug studs off while driving.
I found them at some of the used tire dealers and all wanted $5 per ring and that was for used plastic ones. I then found them online at
http://www.discounttiredirect.com/direct/home.do Click on Wheels then on the next page on Wheel Accessories. They had them listed at $15 for a set of 4, but on the phone told me they were only $5 for the full set with free shipping. The ones I received were metal, not plastic. Now, you can't beat that with an egg beater.