Since “America’s Got Talent” judge and Larry King replacement Piers Morgan said “AGT” runner-up Jackie Evancho, age 10, was a “mini-me” of 30-year-old British mezzo-soprano Katherine Jenkins, there have been whispers that the blond-haired, blue-eyed look-alike pair could sing together in the future. A rep for Jenkins now confirms they’ll perform a holiday duet together at the NBC Christmas Tree Lighting ceremony Tuesday in Rockefeller Plaza. No doubt they’ll make beautiful music.