The linked Wikipedia article seems to indicate otherwise... And, indeed, it looks like the company both exists and has an online store.

http://www.ankerstein.de/

http://www.ankerstein-onlineshop.de/

According to the wiki page they're still manufactured and are widely available in Germany.

From the description in Wikipedia (quartz sand, chalk dust, and linseed oil) it doesn't sound like they'd be too hard to make.