I just built a Kegerator for a 5 gallon Cornelius keg in a Kenmore mini-fridge. I found the height and diameter of the keg first before I looked for a fridge. You should do the same. Also, determine where the coolant lines run. I realized, after I purchased my fridge, the lines ran through the freezer tray. Not the end of the world, it just changes the thermostat control; how fast and how cold it gets.
Long story short, look for a model with a flat bottom inside that fits the 1/2 sanke.
Hope this helps,