I noticed on the weekend that Kmart is selling a bitching mortar and pestle for $12. Its 19.5cm across, so is plenty wide, and is made of polished granite.
I've never seen a large mortar and pestle this cheap before. Additionally, the granite surfaces of the mortar are finely polished, making it easier to use than some cheap mortars that are non-polished. I bought a crappy one from Target recently and it is non-polished and bits of cinnamon bark get caught in the pits of the mortar whenever I use it. Man, I could really grind the crap out of that cinnamon with this baby.
There were plenty instore at the Toowong shop I went to.
The only slight drawback is that at 10cm, it may not be as deep as you would like your mortar to be.
++ for obvious, overriding love of cinnamon