Sorry, can't find my receipt to the Chemical Supply place I ordered from. However, I did find it over the net and ordered 5 lbs from them. Look under chemical supply or pyrotechnic supply (just don't order those 55 gallon drum sized containers from that place in India - the wait is terrible
). You could also look into getting waterglass as an adhesive for the cartridges. Stay away from glues which leaves deposits which abrades the barrel.