I made my own. It was fairly cheap, I think I spent ~$20 on it. I found an old cooler and cleaned it out. I used bleach and let it air out for a few days. I bought an electric box (28 cents at Lowes) and a water heater thermostat (~$9.00 Lowes). I had an old lamp and some screen/screws. I had to purchase a thermometer with a hygrometer ($7.00 WalMart). I drilled some holes in the sides of the electric box and zip tied my fan (woops, it was free, found in an old computer) to one side to suck air across the thermostat. I wired the lamp to the thermostat and I found a wall wart that would run the fan. I ran the wires out the drain hole in the cooler. I attached the box to the top edge of the cooler, the light hangs below the electric box. I wanted it in this configuration so that the light would not shine directly on the thermostat. I wanted to measure the temperature of the air. The fan pulls air across the thermostat so that's what I am doing. I added a piece of salvages screen to separate the lamp and water pan from the chicks. I didn't want anyone to get in the water and drown. If you have to buy all the parts, of course, it will cost more and you will probably be better off buying one.
