You know. The foam board stuff like R-max (http://"http://www.rmaxinc.com/wall-eco-max.asp")
All I can find is 3/4" at Menards, but I want more like 2 or 3"... Lowes? Home Depot?
No, I haven't called my local lumber yard yet, as I know it'd be a special order and they'll charge accordingly.
Dow makes it I found out today- maybe they have supplier near you