Not gonna happen for $100 unless you go used. Your best bet is to try and chase down a Samsung ML-4500 if you can find them. They are discontinued, but you should be able to nab it for under $120 IF somebody has them in stock.
Next best bet is for a Samsung ML-1210. I've seen them going for under $150. You won't find a laser printer for much, if any cheaper than those two.