I am using an old guinea pig cage...the type with a wire top and plastic bottom.   It keeps the four inch deep shavings in, provides many spots for a clip-on heat lamp, and is sturdy enough to hold the bricks I have holding the water/food dishes above the shavings.  Easy to clean, reasonable size, an practical, little to no prep time for the next batch (other than decon time).
       it's the perfect solution for 22 bantams and five ducklings!!