The original box was made by the band FM3 who actually used them as their only instruments when they performed. I saw them once a couple of years ago in Copenhagen.
The used to sell the box from this web site :
http://www.fm3buddhamachine.com/
An alternative is the ones you can buy at dealextreme :
http://www.dealextreme.com/search.dx/search.jukebox
But the sound quality in those are not near the quality of the original FM3 box.
Building one your self would be rather difficult i think, but it coyuld maybe be done with some of the voice recorder IC's availabe. for instance: http://www.winbond.com/hq/enu