My mother just came back from Japan and brought me back a bunch of supplies that I really needed!
I prefer to use only these Japanese brands of clay because there is really nothing else like them! You can purchase them online but they are much less expensive if you can get it direct from Japan. A 900yen (around $9) bar of clay will cost you $25 plus shipping through sellers on Etsy and clay suppliers.
I am well stocked now! Stay tuned for new sweets!