I travelled for six hours with my hamsters (six of them at the time) in small pet carriers. Lots of fitch bedding some cucumber and ... they were totally fine.
A cat carrier sounds huge for a hamster! Mine had guinea pig carriers (that seem waay too small for guinea pigs imo).
This kind of thing but not from pets at home as I dont like their breeding ethics.
http://www.petsathome.com/webapp/wcs...animal-carrier