Need to make thermostat for DIY incubator

[trilinearmipmap]

I need some help from someone who is good with electrical stuff.

I made DIY incubator to grow live food in. It is made from an old mini-fridge which I installed a 15 watt light bulb in.

The problem is it gets too hot and cooks everything. I tried a lower wattage bulb and it gets too cold.

I need to rig up a thermostat to keep the temperature about 75 degrees plus or minus two degrees. Any idea what type of thermostat I can get and how to install it?