* Third Point raising $500 mln-$1 bln to buy Sony stock -sources. : TOKYO (Reuters) - Sony Corp shares surged more than 7 percent on Tuesday after a Reuters report saying Third Point LLC was again raising its stake in the Japanese conglomerate stoked speculation that fund owner Daniel Loeb was preparing to agitate for more change. Third Point, which has about $14.5 billion in assets under management, is raising a dedicated investment vehicle targeting $500 million to $1 billion in capital to buy Sony shares, people familiar with the matter said.