I have heard that bituminous can sometimes be gotten in Duluth, but the guy I heard that from was less than impressed with the quality. I don't know any of that first hand, so take it all with a grain of salt. On a different note, I've heard nothing but good about the Northern Minnesota Metalsmiths (the club itself, not just their coal). Might be worth contacting them; if you can't buy their coal, they might know another source.