Even on a long trip, it's generally considered safer for hamsters to be in a smaller space such as a carrier rather than anything larger and from my experience of travelling with hamsters, they usually go to sleep anyway so don't need a great deal in the way of toys.
The one frequently recommended is the:
http://www.petsathome.com/shop/en/pets/aladino-carrier which I don't know about the availability of in the USA but the link should at least give you an idea of dimensions.
A travel cage is more likely to be used if you're staying somewhere overnight with your hamster. I'd personally use things like
Wilko Fish Tank 10L at wilko.com as my hamsters seem to feel more secure in smaller spaces but if I was going away for longer I might be looking at something a little larger. Depending on what cage your hamster has and what space you have in the car, you could use their own cage.