I think they can be found on ETSY.com. I was trying to find the artist for you but it was taking me a long time. My suggestion is to go to ETSY.com and type RESIN RINGS in the search bar. You can do the same in Google. If I remember correctly when I did run across them, they are a bit pricey.
Found the link but vendor/seller is in Germany. These babies aren't cheap but enjoy.