One of the fashionable girls at work approached me about mani rings yesterday... and I admit I was like "dafck you talking about??" She showed me this Daily Mail link and I was like, "oh I understands!"
ASOS. I found this triangle ring, but it doesn't look quite as secure as I would like. Well, if it does fall off, it was only $11.
KarmaLoop for $38. A bit scary for my tastes, but certainly standout!!
Then I hit almost jackpot with this find at Sephora. Very high quality, looks secure and on sale for $11! I just wish there were more colors!
Etsy for $19. There's acutally a decent number of options on Etsy, so go forth and search for "nail rings" and see what tickles your fancy!