The fridge isn't really a fridge, more like a formica coated cooler.  the hole in the back that looks like there should be something there.... that's where the water tank is supposed to be.  good luck finding an original for less than a king's ransom.  Not sure if there's a substitute that works, something should.

If you've got the tank, you're good to go.  The drain goes out the floor under the cabinet, and i always just used ice packs in mine.