For young corns I use 5 litre really useful boxes. ( Really Useful Products Ltd - Select country ) You can buy them at Staples or Macro.

They have clip on lids, which mean no escapes, but you do need to make some air holes in with a soldering iron or drill or something.

Personally, I am very wary about keeping any snakes together, but hatchlings especially can be cannibalistic, and are best kept seperately. This will also help as if one gets ill, or regurges it's food and they are kept together, you might not know which one it is. If you do keep them together you need to make absolute sure they are fed seperately.

Snakes aren't social animals, and whilst they might tolerate each other, they don't enjoy each others company.