Contrary to what's been said above, Das Pronto isn't actually clay — IIRC it's some kind of very fine fiber material that you can mold and shape like clay
If you wet it with water, you can stick parts together; if you don't use water, the parts are likely to fall apart once they harden. As said, it dries to the air without the need to fire it, but it's not as strong as fired clay.
If you want it in the US, you could order it from this webstore
(probably among others), a quick websearch tells me.