I know that it isn't easy, but cast your mind back to those hot summer days. Remember how your maggots died in the heat, how the lucheon meat went soggy, and how the cold drinks weren't cold.
Here's the answer. A really smart cool bag from Shakespeare. It measures 14"x10"x8" deep, has an all round zip, plus a small top zip that you can open to remove bait without letting all the cold out.
The bag is lined with a reflective material, and just needs the addition of a couple of freezer blocks to give you an ideal bait keeping system.
Ideal for boilies, frozen deadbaits etc also.