Feiffer wrote the Great Comic Book Heroes and is responsible for one of the best analyses of Superman (from that book) and has done many comic strips about Superman but I've never heard of this play. He is a great playwright and screenwriter --maybe the play is hidden in a collection of his one-acts?
My favorite quote from THE COMIC BOOK HEROES:
"Why is it that for all of her vaunted Amazon power, I could never imagine Wonder Woman lasting one round with Sheena, Queen of the Jungle?" Good question!