My husband came up with this idea for our son.
We bought an ordinary outside garbage can (take your child with you to make sure that the can will be big enough but not too big). We cut out the bottom so he could walk. We then spray painted the outside to make it look like it belonged on the curb.
To keep the top on, we took an old bike helmet and screwed it to the top. He then wore the helmet and didn’t have to worry about it slipping off.
To keep the can on, we put elastic straps on the inside, criss-crossed so they wouldn’t slip off. They were also screwed to the can.
My son would put on the can, ring the doorbell, then crouch down in the can and jump up when someone would answer the door.
He was a huge hit at school. It was very cheap to make since the can cost about $15 and a couple more dollars for the elastic. Otherwise we had everything else!