I don't know if there is a name for what you're describing other than to call it "a crystal on a piece of fishing line".
Where to find one is equally as ambiguous. I see them in places like card shops, gift stores and drug stores. There's even a little "mom and pop" Mail Boxes Etc type of place by my house that has a display full of them in all shapes and sizes. If you're really stuck, you might want to try a New Age/Metaphysical shop which you could probably find by looking in the Yellow Pages - they're sure to have loads of crystal things.
Good luck!
.....Kelly
