The actual sensor element itself is made by a company called Nicera under the part number RE200B. Here is their site http://www.nicera.co.jp/. Unfortunately, the only people I have found that sell the sensor are http://www.mpja.com and http://www.glolab.com. I tried to contact Nicera about buying a bunch of them and had no success. They only sell in lots of 10,000.
I ran across a page a while back that had some data on KDS PIR elements, but I couldn't find it on Google when you posted this message. It crossed my mind again tonight, and I looked again... this time it came up. The URL is: