Sept 28 (Reuters) - Hair products maker Olaplex Holdings Inc, owned by private equity firm Advent International, increased the price range for its U.S. initial public offering and is now seeking a valuation of up to $12.3 billion, a regulatory filing showed on Tuesday. (Reporting by Sohini Podder in Bengaluru; Editing by Amy Caren Daniel) Our Standards: The Thomson Reuters Trust Principles.