Not sure if this has been done before, but what about some old time hints and tips that our grandfathers, fathers, mothers etc used when they were camping.
When dad didn't have any ice, he used to grab a handful of course salt, throw it in a bucket, half fill with water and put in a few beers. Half hour later, nice cold beers.
I can still sort of picture the old Carbide Lights too, but can't remember how they were made.
