You can get them for around $40.
Keep in mind, these things can consume a lot of energy and produce a ton of heat. Because of this, it's recommended you run a dedicated PSU and cool it with liquid.
Going from the above link, a 226 watt (heat capacity) TEC can draw 25 amps by itself. The heat it produces it 226 watts + whatever your CPU puts out, in the links example, 60 watts. The total heat output would be 286 watts, good luck air-cooling that.