It really depends on where you buy all the parts. The easiest, though most expensive route would be to get AdaFruit's LED belt kit ($60) - http://www.adafruit.com/products/332
The suspenders were $10 and I think the "wool" cost me around the same.
Then you'd have to slice the LED strip in half and rewire it like I have. You can get additional 4-pin JST connectors from adafruit as well, you'll just need to wire up a Y-splitter.