Dont know if this will suit, but considering the exchange rate is tremendous, have you ever considerend just renting a car from ny and driving up?
Driving in upstate new york in particular is relatively stress free (im from ny by the way) and if you have the time to spare, it'd be a blast really. It's a fairly long drive from nyc to niagra, but there are ways to break it up: its cheap on the bus (greyhound) to get to albany, rochester, buffalo) and then rent a car.
part of the fun of the states is driving to be honest.
cant recommend any tour operators, but if you want something a bit different, there's always a way (my opinion anyway)