I bought some at Michael's (Craft Store) nearby. Else - i think some LFS sell slate rocks, which seem to work pretty well for breeding fish also. My jewel cichlids liked the slate better, but that's just their preference.
Go to your nursery or hardware store. They will often have many things for planting things, thus having clay pots in all sizes. Just rinse them with hot water and plop them in the tank.