Concentrate on a replacement fridge - check out Refridgerator and Freon on Wikipedia.
Whatever the gas is in your machine it's a sealed and pressurised system and will be very very difficult for you to repair without extensive workshop equipment and plant.
In the mean time - the ancients made ice in the desert - insulate a stone area from the sun with straw and an awning during the day and at night (if there's no cloud) run a thin layer of water over the stone- Collect ice in the morning and store in an insulated cold chamber.
http://yarchive.net/space/ice_in_desert.html
Peccavi
November 2008