i've also been wondering where to buy that stuff. i went straight to the homesew site; did a search; only found one kit. i googled "insulbrite" hoping to find it by the yard. nuthin'. i found 2 measely yards on ebay. i didn't buy it since this is a "someday" need for me. didn't want to ace out somebody who needs it now.
http://cgi.ebay.com/INSULBRITE-HEAT-RESISTANT-BATTING-FOR-HOT-PADS-AND-MORE_W0QQitemZ360001257646QQihZ023QQcategoryZ4836Q QrdZ1QQssPageNameZWD1VQQcmdZViewItem?_trksid=p1638 .m118
i did a little better when i googled "insulated batting"
http://cgi.ebay.com/36-x-45-Insulbright-Insulated-Batting-for-Potholders_W0QQitemZ180136350466QQihZ008QQcategory Z116679QQrdZ1QQssPageNameZWD1VQQcmdZViewItem?_trks id=p1638.m118
http://www.ericas.com/quilting/batting.htm
http://www.candflinks.com/store/insulation_batting.html