One item that is a must have for your cat is a cat carrier. Your cat will have appointments to keep and will be safe when traveling in his carrier. This will come in handy many times over through the life of your cat, but this is especially true for visits to the vet. A cat can be skittish, especially with other animals around, and you do not want to be scratched and clawed up because you did not have a cat carrier.
Just looking on the internet shows a wide variety of pet carriers. You can buy purse style, pouches, backpack types, soft-sided carriers, hard-sided, and even hounds-tooth varieties. It is probably best to look for one that is ultra light so as not to make it too heavy for carrying around easily. This is very important if your cat is a little on the hefty side.
If your cat does not want to go in his cat carrier it could prove difficult to make him. The simple way to do this is tip the carrier with the door opening facing the ceiling. Grab your cat gently using two hands, I would have one hand around the legs to avoid scratches if they kick out, and gently lower then into the carrier feet first. Close the door fast before he gets back out and make sure the lock is closed tightly and securely.
By using a cat carrier you will be keeping your cat as safe as possible while traveling, while protecting yourself from bites and scratches too.