Dell and others have such units but you need to look at them and find out if they offer a bigger battery.

-> That battery time is usually whacked down as the laptops head towards production. If the engineering team gets 10 hours on the stock battery the trip to production carves it back to 2 to 4 hours to achieve a lower price. No laptop save two I know of (which don't meet your specs) go much longer than 4 hours without custom ordering it with the big battery.