I've been looking all over the Arduino website and online but I still can't find out where to buy it.
I am in the same boat, I am interested in purchasing one but I'll be darned if I can find a link to do so.
For what I know, the printer is unfortunately not on sale anymore from Arduino.
You should however be able to buy it from Sharebot, the company that actually produces the Materia 101 printer, under the "Kiwi 3D" name. This is the link for the kit version of the printer: http://www.sharebot.it/index.php/product/kiwi-3d-kit/?lang=en
dp_1