I use a 55 gallon rubbermaid bin - I cut large square holes in the lid then fixed wire mesh to the lid so I can simply set the heat lamp right on the metal wire mesh. I use 100W red-colored flood light bulbs to heat the brooder. I'll take a better photo of my setup to post later but have one for now that shows the brooder close-up.
Most important thing is to contain the water - cut a round hole in a gallon plastic juice or milk jug, this will prevent the ducks from splashing water all over the brooder. Works very well and costs nothing. I installed metal L-brackets into the side of the bin so that I can set the food container on it. This keeps the ducklings from soiling the food container since it's up off the bedding.