I finally got it! My CK moonstone ring! It is just as fabulous as I had imagined!
I bought it at Klockmaster Hansson, Frölunda Torg. They were very helpful and nice, they ordered one with the right size and transparency (they are way cooler when you can see through them). This morning they called me and told me that I could come get it. I sure have a weak spot for personal service.
Note: I do NOT mean the kind of personal service when the staff attack you at the door to ask if you need any help, or open the fitting rooms to "see how you're doing", but the plain niceness that you sometimes encounter that will brighten your shopping experience.