I'm a fan of the products sold by Kuroki Goishi Ten. I noticed on their site today that they've launched a (Japanese-only) blog, and an outlet site (with English translation) for their stones, at some discount.

The blog is here: http://igo514.blog133.fc2.com/ (not much there yet).

The outlet site (English home page) is here: http://goishi.com/eng_index.html

(I'm not affiliated with them, and haven't bought from the new site. I have bought from Kuroki Goishi Ten before and have always been happy with their products and service.)

-M