As it would look in granite, maybe - option not offered by Shapeways ;)
Ring with small loose ball in twisted cage. Inner diameter is 18mm, band is 2mm in diameter, and the ball is 2.2mm in diameter. (The ball is printed with clearances not shown in the renderings, where it is shown lying at the bottom of the twist.) Can be done in other sizes - let me know if you're interested.
2.514 w x
2.338 d x
0.99 w x
0.92 d x