Cut a green circle from a foam sheet for the base just about 1/2" to 3/4" wider than the cup, a strip of black foam sheet about 1" to 1 1/2" wide for the band, and a yellow rectangle, about 1/12" to 2" wide, with the center cut out. Cut a small shamrock from the green foam sheet. And you will need a small piece of gold tinsel stem.
On the cup, affix the black strip and yellow buckle near the opening of the cup and secure with hot glue. Fill the cup with the candy of your choice and then put a bead of glue on the rim of the cup and position the green circle onto the rim. Glue the shamrock to one end of the tinsel stem.
After the glue has cooled turn your cup over and insert your tinsel stem into the band near the buckle.