Where did Kristen Stewart get her moonstone ring for the twilight movies?

The moonstone ring Bella Swan (Kristen Stewart) wears in the Twilight movies is a prop specifically designed for the films. It wasn't an existing piece of jewelry.

The ring's design was inspired by vintage rings and was meant to symbolize the connection between Bella and Edward. It's a beautiful piece of jewelry, but it's not available for purchase as a real piece of jewelry.