Preferably like one in this video. [ame=http://www.youtube.com/watch?v=Xq76j8LBO3k]YouTube - Electro House 2010 (WICKED MIX) DJ BL3ND[/ame]
Spencers.. I live in the city so alot of music/audio stores have whole stage lighting sections. Id probobly go there if you want a good one that you could actually control. But if you want a cheap one for personal use just go to spencers
As far as syncing with music, youd need a whole setup to get that to happen...neatly anyways. You could try looking for sound activated lighting fixtures. Some of them need a DMX board, but others just wave around to the beat of the music.