This is also one of the simplest things to make.
White TOP OR White cardboard
Yellow Paper OR Yellow marker or sketch pen
Thin wire or white thread/ribbon
Devil horns from party city: http://www.partycity.com/product/clip-on+devil+horns.do?refType=&from=Search&navSet=devil%20horns&bypass_redirect=1
If you use a white top, cut yellow paper in ovular shape and stick it onto the top using fabric glue.
You could just cut white paper into ovular shape and make a yellow yolk in the center using a yellow marker or sketch pen. Pierce holes into the white cardboard using pins and tie a thin wire through the holes. This will help you tie it around your neck. You could use ribbon or a white thread instead as well.