Thanks everyone - That's actually quite a good idea to convert a normal cool box (in Australia we call it an 'Eski'...) to a fridge. The Isotherm stuff is still pricey though. When I say 'peanuts'... I mean like $50!!

Maybe I should be looking at 'auto fridges', since anything boat related has an instant 50% markup? Surely in the caravanning arena you can get a secondhand fridge pump for next to nothing?