Can’t get a ticket to “The Producers” on Broadway? Then you might consider heading out to Los Angeles, where “Gilligan’s Island: The Musical” has just opened, following a sold-out engagement in San Diego. Former Batwoman (in the 1966 “Batman” movie) Lee Meriwether, 66, plays Mrs. Lovie Howell alongside her real-life husband, Marshall Borden, who plays the millionaire Thurston Howell III. Grant Rosen stars in the leading role of the light-headed Gilligan. The creators of the ’60s TV sitcom (which remains in syndication) are behind this musical version, including series creator Sherwood Schwartz and his son, Lloyd J. Schwartz. The music and lyrics are by Laurence Juber and Hope Juber. According to the show’s official Web site, “The castaways are stranded, Gilligan finds parts of a rocket which the Professor assembles. The Howells help write a note to put in the rocket nosecone, with island coordinates given by the Skipper. The girls (especially Ginger) help ‘motivate’ the Skipper to peddle a rocket launching device to speed . . . (and) the rocket is seen by a group of extraterrestrial aliens.” All set to music.