Dear Ilija and Randy,
Here's the link of the German company selling the Thuringian stones:
http://www.mst-mueller.de/index2.html. On the left upper corner of the web page you click "neue Produkte" to see the stones and some sample sizes and prices.
I understand from the forum dicussion of NassRasur.com there are more (larger) sizes available.
I am actually considering ordering one.
Randy, can you get me in touch with the member who is looking into these stones? I'll send this Herr Mueller an e-mail asking him to give me more details of the stones and let you know when I know more.
Living within the EU it is easy for me to order them without having to pay additional taxes and excises.