We recently added a new product to Etsy: Double Looped Silver Plated Stacking Ring, priced £4.00:

[Description from Etsy product listing]

A single double looped stacking ring, made from silver plated copper in 1mm thickness.

The ring comes in one size and can be adjusted for a better fit as is has an open back (please see photos)

 

Find it on Etsy here