(Reuters) - Sportswear retailer Frasers , formerly Sports Direct, has bought a 12.5% stake in handbag group Mulberry pushing ahead with plans to move upmarket into the luxury business.The purchase makes Frasers, controlled by British billionaire Mike Ashley, the third biggest investor in Mulberry, based on Refinitiv data. Frasers was created when Sports Direct unveiled a rebranding in November to reflect the group's broader range of products, including new Frasers luxury lifestyle..