4x12" piece of Saral Red Transfer Paper. This wax-free transfer paper is designed for ceramics, and it what I use when transferring designs onto linoleum to make molds / texture plates. You could also use it to transfer directly onto leather-hard metal clay.
If you need large amounts of this item, you can buy directly from Dick Blick. I'm just listing this small size here as a convenient way to try it out (although it will probably last you quite awhile as it is resusable!). Ships free with another item. Have fun creating!