It has from the start been offered by its inventor as a download for 3D printing (see the "About" section of the official site); it is also commercially manufactured, and available from Amazon. (See link from official site; if you don't live in North America, follow the link and then change the ".com" to the suffix for your regional Amazon.)
There is also an "X2-Cube" (3x7x7 with a 2x2x3 column omitted from each corner) and a planned "X-Cube 2" (2x4x4 with omitted corner columns).
A different "Super X-Cube" (same shape, different colours*, possibly different mechanism) was designed by Aleh and Evgeniy in 1989. It is available from the HK Now Store and from Meffert's Puzzles. Tony Fisher also designed a puzzle of this type.; scroll up to the first post in the thread
*Both X-Cubes have the traditional colour arrangement (red opposite orange, green opposite blue, white opposite yellow), but the first one on this page has white-yellow as the 5x5 faces, whilst the other one has red-orange.
MechanismEditThe X-Cube is essentially a shape mod of the 3x3x3. The X2-Cube has more freedom of movement, but not much more due to internal bandaging; it handles somewhat like a Professor Cube.