I have a case which opens in 2, and has 4 lights in each half, a lead conects the halves, and a kettle lead plugs in the mains. Small and portable, but effective.
The lights react to volume, rather than music (i've noticed) but they do the job, and stop you looking like you're gigging in someone's front room.
They were £40 from the local disco equipment shop - but this was about 5 years ago.
[url="http://www.maplin.co.uk/Module.aspx?ModuleNo=220152"]http://www.maplin.co.uk/Module.aspx?ModuleNo=220152[/url]
this kind of thing, but they've gone up a bit in price.