Hello,
How about this:
http://cgi.ebay.com/Genuine-Thuringi...QQcmdZViewItem
I believe that's like the Escher even though this is Echter. Aren't they all coming from the same quarry? Now whether the stone actually belongs to the box is a whole other story, but may be an expert can seched some light.
Anyways, it's 120+s&h BIN, which strikes me as a bit expensive, although a member spent that much on an escher few days ago.... $1 to open bidding.