I've used the single and dual from Ridgeview Audio on 4-5 guitars with excellent results. I had him make me a triple one I put in an old seagull I had and it worked brilliantly. He also makes (or did) a simple, cheap pre-amp that does the trick quite well.
http://www.ridgeviewaudio.com/mdk12d.html
Great service, great product and a fantastic price.