I got a few bags of Carbon Vegetable Lump Charcoal from a supplier that I know here in Halifax. It comes in 10KG white bags. The bags looks low budget and are very dirty but the quality of the lump inside of the bag is pretty good!
I also did a few 15 hour cook with my fire box filled to the top and at the end of the cook there was still 3/4 of the lump left! This stuff is amazing and burns very clean and doesn't produce that much ashes.