Have you considered a Giant Stilleto, they can be bought with a 3 or 7 speed gear train.
That been said I am tossing up fitting a 21~24 speed deraillier system to one of my choppers, bear in mind you will have to spread the rear triangle to fit derailiers or most hub systems above 3 speed.
Also if you bike of choice has a wider than normal hub you may not be able to fit either option.