Zipties. Often people will bring small zip ties or even tiny padlocks to keep their birds safe from theft overnight at a show. They lock the cage doors closed with them. Thefts are very, very rare.
Wipes. Baby wipes or pet wet wipes can be used to wipe the bottoms of feet off if your bird happens to poo and then step in it, because that’s what they do. For cockerels and cocks that happen to get it on their wing tips wipes are great for wiping that away. They’re also good for cleaning up little messes, like if you spilled or dripped your sweet oil on something.
Food and water. You’ll want to bring food for your birds and their own water. You can most likely find water at the show venue, but if your birds are picky about drinking “strange” water you should bring your own. Save your empty milk/juice jugs and fill them with water from home.
Writing pen. You’ll need a pen to fill out your cage card for your birds. This is the card that has your bird’s information on it like leg band and type.
That’s it! A pretty basic list. As you show you may find that you need additional supplies, see a good idea from a fellow show attendee or even decide you don’t need all of this stuff. If you end up forgetting something someone is usually nice enough to let you use/borrow some of theirs. I encourage anyone even slightly interested in showing to get out there and attend a show. They are really a ton of fun!