On Runescape, what monsters drop granite mauls?

I have decent stats and PK a lot. My attack is level 47, but I'm training it up fast. My strength is needing a little working on to use the maul because it's only level 35. I would like to know also where to get a rune defender, and the best weapon for me right now. I'm using a sacred clay sword for all of the training right now. Please help?