Edit note:
I was also thinking of making a cookie tin heater like the one in the guide I found http://www.the-chicken-chick.com/2011/11/make-cookie-tin-waterer-heater-under-10.html Have any of you made any of these or do you currently use these?
Haven't made or seen a cookie tin heater, but my neighbor puts a 75 watt bulb inside a cinder block and puts the metal waterer on top of the cinder block....it worked all winter last year. This year is supposed to be colder....time will tell if it will work in the extra cold weather