Purchase a $59 play gym, complete with lights and spinning objects if possible.
or. . . Purchase a balloon. Yes, one balloon.
They say it doesn't take much to entertain a child. Buy a toy and the baby will play with the box. Today as I watched beta giggle and chat up said balloon for approximately 45 minutes I realized a) how true this addage was and b) I better start saving egg cartons and empty boxes for the future entertainment to come!