I got my set from Raderwerks along with the wobble bolts. Just give them a call and tell them the bore size you need, and they can get you a set if they have them. If they don't have them, you may try your wheels manufacturer, or eBay. I think mine ran me under $20 for the set. And FYI, just get plastic, the alloy sets aren't worth the coin.

What wheels are you running?