Cat carrier with a litter box?

My cat has severe anxiety problems, and always urinates on herself when I take her places. We're moving across the country, and I have to ship her in a crate that meets the airline's requirements. Is there a crate that is plastic or metal that has a litter box in the bottom? Sort of like a rabbit hutch, with a floor, then a litter box, so she doesn't have to sit on the plane for 6 hours in her own urine. I've searched google, but didn't find anything.