For a 4 hour journey most healthy cats would be OK with just going in a regular sturdy crate/ carrier. Cats tend to just curl up anyway. Something like a PetMate Sky Kennel or VariKennel in the 100 size would be plenty big for any but the most huge cats. Get it with the food & water containers that clip on to the inside of the metal door, so you can pour a small amount of water in.
Put an absorbent pad like a puppy pad, or better yet get a "DryFur" pad (you may have to order some), in the crate. Hopefully the cat will use the litterbox at home before you leave. I would not feed him the day of the trip until you get to your destination.
. For a long trip I would suggest a larger dog crate where there is room for a small litterbox in the back and still room for the cat to lie down in front of that, and of course a water dish, preferably clipped to the side.
Sometimes cats won't go to the litterbox when you offer it to them at a rest stop and then they need to go later. Other times they may go on a 12 hour trip and not need to go at all . It is hard to predict but if I am travelling like 8 hours i would rather they have a place to go when they need to.