Look into whey protein isolate...it's very low in lactose - less than 1g per 28g serving of the stuff I have...I'm not lactose intolerant though so I'm not sure if even that would be too much (compare to 12g lactose in an 8oz cup of milk).
There is too little lactose in whey protein for it to give any symptoms even to people with the most extreme lactose intolerance (absolutely zero lactase production).