BOUNTY OUT FOR EVIL MRS. X

HARVEY Weinstein – the P.T. Barnum of the movie industry – is hyping his version of “The Nanny Diaries” by offering a $100,000 reward to anyone who can identify the bitchy, shopaholic Upper East Side mom (played by Laura Linney) who inspired the authors of the best-selling roman a clef. Manhattan’s upper crust is buzzing over the identity of Mrs. X, who ignores her child and terrorizes the nanny (played by Scarlett Johansson). While the authors refuse to divulge any information, one suspect is Lisa Birnbach, co-author of “The Preppy Handbook,” who once employed one of the writers. At a recent screening of the movie, which opens Friday, Weinstein was overheard promising a few well-connected but tight-lipped socialites $100,000 for any information that would lead to Mrs. X’s unveiling.