Whoops I forgot some stuff (told you I would)
2 small bowls (for water)
1x 2litre bottle of water (can refill at the show, I also carry 5 litres bottle in the car)
1x spray mister (for water whilst in the ring)
nail files (for the dog)
Pooh bags (nappy sacks, both in the car & in the show bag)
and probably some more 'stuff' that you never know you might need.
(Like vet bed/blankets if I'm at a champ show)
If so that's normally means two bags as I also have my packed lunch too.
I also have my mobile phone, purse and breakdown card with me.
I too have a trolley which I take to shows if I take cages.
I've found that the fishing trolley is a brilliant addition to my
show equipment. 1) It wasn't as expensive as some of these
trolleys marketed for showing people. 2) It's designed to go across all terrain cause its for fishermen. So the wheels never get stuck in the field. It's my own 4x4 trolley

The only thing I may need to do is a little adaption and have a little
mesh welding on part of it due to if you haven't got cages then your bags etc fall through.
Oh and another useful thing to carry, folding chairs, as you never know when you'll need one.
In my car I also have the windscreen reflective cover and 2 reflective sheets to put over the car to keep it cool whilst we are at the show.
The reflective sheets also double up in the winter as an underblanket
which I place under the vetbed to keep the dogs warm.
Bungees for the trolley and sheets are in the car.
So I do have quite a loaded car depending on which type of show