I love these too! I got mine on etsy, I found that a few can look and feel like plastic. I originally got mine from asos, but they couldn't fit over my and and when I finally pulled mine over, it was tight on my wrist.
I bought mine from this etsy shop : http://www.etsy.com/listing/98966836/spike-bracelet-renegade-gold-spike made with metal and had weight to them. And they were able to pull over my wrist. And if you get two she gives 10% off using stack10 at checkout, I've used that a few times, I don't think it expires.