You can get a fridge from a used appliance store that has been striped of parts or not fixable, for free or next to nothing just talk to the people who work there and see what they have...

You can get a ranco 111000 from e-bay for $50-$55 shipped and wire it yourself heres a link to good instructions on how to wire it
http://rcreptiles.com/blog/index.php...1000_thermosta
I would recomend a proportional thermostat you could use a Spyder Robotics Herpstat they cost about $109 though....

Flex watt is cheap $3.50 a foot and add some cpu fans in there and the total should be around $100 and about $150 if you get the proportional thermostat...