The site basically said it was her husband's and had a little bit of stuff from Toyo Ozaki herself. I've forgotten how I tracked it down originally, but I think I was looking through a lot of Japanese PS sites and eventually found a link to it.
And today, I have found a really old book mark to the site! Here it is:
http://homepage1.nifty.com/shosi-senban/index.html
It looks a lot different than I remember and there is very little reference to Toyo now that I can find. I did find what appears to be an option to buy a revised reprint of the PSIII artbook! Go here:
http://pro.tok2.com/~ape/shosisenban/cg ... /index.cgi
In the right hand frame, click "ファンタシースターIII" near the top to find the book. The cover is different, but the sample content matches some of pictures I've seen from the original book. It's listed at 800 yen. I'm not entirely sure if this is legitimate, how many of these books they have, or if this shopping cart even works, but maybe it will help someone find the book.