They came from Ringmaster9511 on Ebay here and they are certainly reasonably priced, in addition to the Frankenstein and Creature he also makes and sells rings of
Go and check out his stuff, believe me the pics do not do the rings justice. They have a nice solid weight to them and have a feel of quality I haven't found in a "biker" ring in quite some time and believe me I have quite the collection of the type of rings that usually fall into this category. The details in theses make them works of art, from the warts on the Creature to the neck stitches on the Monster you can feel the level of artistry. The artist said he's going to try and add some more monsters to the collection, hopefully a Bride and Metaluna Mutant.