um ... thought the cat's name was Tavel - perhaps you might edit your post to say tRavel?
And we have a few folks on board who travel.
You want to get Diabeto used to the carrier/crate, and have one big enough that he can stand up completely, turn around easily, and lay down comfortably. Leave it sitting out with a comfy blanket, maybe spritzed with some Feliway spray or sprinkled with catnip (if he likes it. Once he likes hanging out in it with the door open, introduce having the door closed, being picked up, walked around the room a bit, then put down, and released. After 'bout a week of that, extend this to going to the car and taking a short drive, returning, and releasing him. Low carb treats after each teaching session. If you've a friend all can visit, take him to visit with you to give him the experience of new places.
Teach him to wear a harness and leash, so that if you are flying or in a new environment, you can hang on to him. Again, this is a process of small steps - put it on for 20 min or so with low carb treats, then remove. Gradually increase the time. Add in being in the carrier with the harness, and trips. This will help if flying - airport security may ask that you remove the cat from the carrier - in that event request going into a small room for the cat's safety as even with a harness, it is possible for a cat to be overstimulated and bolt.
If driving long distances, use a 30" wire crate which will fit in a modest litterpan as well as having space to lie down and maybe even a water dish.
Have all vaccinations up to date and prepare a folder with his info and current, signed rabies certificate. Make sure he is microchipped. Have several current photos, expecially of identifying marks. Locate vet offices where you are planning to visit, just in case you need one. Also locate pet food supply resources and their hours where you are visiting, so if you need something, you can get it.
A cooler for the insulin and cooling packs to keep the temperature controlled. Syringes, testing equipment, hypo supplies, food, etc.
Basically, you're packing for a diabetic "baby" going on your trip.