What you want to buy is a good quality 10 or 12 inch ceramic flower pot with two saucer. We'll get to why you need two saucers for each pot later. You will also need some sand, enough to nearly half fill the pot. This is all you need for the grill. Of course you will also need charcoal and some skewers, as well as something to cook, but the grill is done.
Warning: I said that the terra cotta of the flower pot will insulate your grill. This doesn't mean that the pot will not get hot. It will get horribly hot and should be placed somewhere stable and safe. At all times someone should be responsible for each pot you put out and at all times until that pot's fire is extinguished.
A good pot shouldn't have any cracks. Cracks can cause your pot to break when filled with burning coals, and that would be bad.
