By Lewis Krauskopf NEW YORK, Aug 10 (Reuters) - As inflation worries ease, U.S. stocks may need a fresh source of fuel to propel further gains this year, investors said. But with many traders now betting the Federal Reserve is unlikely to raise interest rates again this year and fears of a U.S. recession receding, an improving inflationary picture may become less of a driver for stock prices going forward. Individual CPI reports have not had "a material and lasting impact" on markets for several months, said Guy LeBas, chief fixed income strategist at Janney Montgomery Scott.