Movie star and beloved cowboy Kevin Costner is going the extra mile when it comes to his appearance post-divorce, according to a sensational report. Fans noticed what appeared to be bleached blond locks and a thicker hairline when Costner, 69, stepped out to debut the first film in his four-part Western epic Horizon: An American Saga at the Cannes Film Festival just weeks ago in May, RadarOnline.com has learned. “He fusses over his hair nonstop and is now getting weaves,” a source close to the star told The Globe, alleging that he is “dabbling in other beauty treatments like Botox and spray ta…