Where can I buy a ruby cube?

Do you mean a Rubik's cube? if so, they can be bought at almost any online store:

http://i279.photobucket.com/albums/kk129/nick2272/rubiks_cube.jpg


http://www.play.com/Gadgets/Gadgets/4-/181736/Rubik-Cube-Classic/Product.html



http://www.amazon.com/s/ref=nb_ss_gw?url=search-alias%3Daps&field-keywords=rubix%27s+cube