My sister used to have a keyring like that. I'll ask her where she got it. If I remember correctly, though, you might not want to order that one, because she said the balls kept coming unscrewed.
Tiffany has them actually. Also, White House | Black Market (a women's clothing store) carries keyrings with dangling stuff on them that you can easily remove just to have the keyring.
Although Tiffany is expensive (and not worth it for a keyring in my opinion) you can try Etsy.com for something handmade (as someone else directed me to earlier this week).
My sister used to have a keyring like that. I'll ask her where she got it. If I remember correctly, though, you might not want to order that one, because she said the balls kept coming unscrewed.