you might have me on that one.
I just take it from my chemistry department. You can buy it commercially though.

20 kgs dry ice, 50 kgs ice, 5 kgs salt topped up with water does a bath and it lasts most of the day.
( the mighty badger Aphrodite, on a bar stool, by your side, Fri 12 Jun 2009, 16:19, archived)

what if i want a bath?

( Sir Sand GOBLIN ^popular page dis, Fri 12 Jun 2009, 16:21, archived)

you would be very cold

( Tyronne Get To Falkirk, Fri 12 Jun 2009, 16:22, archived)

I used to have a spare bathroom for beer cooling purposes
I kept the lawnmower in it the rest of the time.
( the mighty badger Aphrodite, on a bar stool, by your side, Fri 12 Jun 2009, 16:24, archived)