Scrutinize your script while making a list of all props that are absolutely necessary for the telling of the story. This is your primary list of props.
Reread your script while examining your scenery sketches to decide what you would like to add to enhance the set. This is your secondary list of props.
Remember: don't decorate just for the sake of decoration. The audience needs to concentrate on the play, not the scenery and props.
At your initial group meeting with your cast's parents, give each one a copy of your primary and secondary lists. Explain the differences.
Ask for parent volunteers to coordinate the collection of props. This is a perfect job for a parent who is a little leery of costumes or scenery.
Attics, garage sales, and thrift stores such as the Salvation Army Thrift Store are places to look.
Still stuck for ideas to get a certain prop, contact Theatre4kids for advice.
Remember Shakespeare's words: "The play's the thing...." Only use props to enhance the telling of the story.