I have already bought it.

Trust all of them, giant? They are sold in supermarkets.

Append:

The foam cooler box is standard size. But if you want something smaller, and it's for food, you might as well use a refrigerator.

It's the kind of incubator that people take outdoors for picnics, so there are many choices. Square, round, big and small.

Griant, Tesco or any store that sells outdoor sports and activities.