The standard answer for this is Bigfoot. They make a 25', but it's probably not the floorplan you are looking for, and they are very expensive.
When I was originally looking for a decent cold-weather RV I quickly realized that a truck camper is the best option for truly capable winter rig. It's an enclosed box vs. TT's which usually need to compromise on the underside to deal with running gear and plumbing. Also, towing a 26' trailer on icy roads isn't going to be as easy as driving a 4wd truck with a camper on it.
