That 70mm fan linked to is a bog standard computer fan and, IMO, is over priced. If I was doing this, I would opt for 2x 90mm case fans or 3x 80mm fans. They are easily ganged by a small strip of metal and fastened with through holes in the metal. Somewhere in the back of the fridge, you should have a 12V supply termination or wire. Splice into that power source for your fans. Sometimes, a switch or potentiometer and switch is a nice thing to have in the fan power circuit. That allows a user to control fan speed and on/off function.
