Would those $6 Big Lots computer speakers work for you? They do have an on/off switch.
Yes, those are what I used in my MiB and they have great sound. The werewolf in my video upthread is using those speakers. You will have to find a place for the sub-woofer and there's a bunch of wires to deal with, though. I paid $50 last year at MicroCenter.Go to eBay
I just bought a set of Logitech x-240's for $25.
They sound incredible!