If you can plug in heat lamps (not recommended by the way!), then you have electricity and can plug in a heated waterer. Much better than heat lamps, those are a fire hazard and not necessary at your temperatures. Heated dog bowls are the best - easy for the chickens to use, easy for you to clean and refill, inexpensive (compared to other heated waterers), and all around great. The golf ball trick only works if the balls keep periodically moving, and if the temperatures don't drop too low. Kind of like how streams and rivers (moving water) are the last to freeze, but they too can freeze if it gets cold enough, so it will take a lot less for the gently bobbing golf balls.