air dry clay & other materials

[Powder]

Where can I get air dry sculpey? Someone mentioned it was one of the best items to use for customizing. I tried another air dry clay but it crumbled once it hardened. Any tips/suggestions about an add on material to shape areas of a figure would be great. Not for serious use but more for practice, Ive been using crayola model magic lmfaoo... for throwaway figures its actually serving some use. Im just doing it for experience, ya know, shaping, not leaving finger spots & all that. Once it 'hardens' if you could call it that, i paint it with crazy glue & so far its held up. Now that Im getting a little better with that I wanna do some serious business. Help!