This works very well for us so thought maybe it would be useful for my BYC family. My DH and I made this heated bucket stand for our main coop. The bucket is a rather short 3 gallon one from the bakery (free), turned upside down, spray painted dark green with that Krylon spray for plastic to darken the light, a caged work light with 25 watt bulb goes through the side and is wedged so it won't slip out or go too far into the bucket. It keeps the water high above the shavings and keeps it from freezing (we went to 3 degrees and it only had a tiny skim of ice on one side of the tray). Some of the paint has been scraped off to allow a tiny bit of light, so it also serves as a nightlight. Just be sure the bucket is a sturdy, heavy one.
The worklight is one of this type:
The worklight is one of this type: