For the hub rings, discounttiredirect.com has them for $15: http://www.discounttiredirect.com/direct/brochure/accessories/tmpAccessoriesWheels.jsp
I only say them as their customer service is excellent. I bought my wheels from them 3 years ago, called them, and said I lost my hub rings, and they sent me a new pair. No charge. And they are metal, aluminum I assume.