For short trips car trips, we got Simba something like this:
But for longer ones (Which we haven't had to do yet.) We have something similar to this, where we could have a water bottle attached and all that fun stuff.
We got the soft sided one from PetSmart and the hard one we bought off of someone, but the pictures are both from the PetCo website (One in the small animal section, the other in the cat section.) I hope that helps.