New Style Stove Hoods
I've got a new Airstream and a Sparestream! Both have the hoods that hang below the cabinets and yes the fans do vent to the outside. Yes they are noisy too, but I do turn them on when cooking to keep the smoke detectors from going off.
The outside vent is covered, and has a light weight plastic "flapper" that can be locked closed for travel. When you run the fan, it pushes the flapper vent open.
First, I doubt these hoods are all that expensive, and second, I doubt if the exhaust would exactly mate up with your current outside vent, but any half way decent ductwork shop should be able to make a small duct that would run up the back of the hood to your existing vent.