Searching for a story about a ring and an amulet of transformation

I all.
I'm searching for a story, I think it is related to the Spell'r us world.
A man buy a "kit" composed by a ring and an amulet the amulet allows to change who wears the ring in any way.
The story compren many type of transformations.
Till now i was unable to find it, the only ring related story of the sru world i was able to find is a complete different story.

Do anyone know where can i find it?
Thank you.