This year, Britain's Royal Ascot, the world's most storied summer horse race, marks Queen Elizabeth's Golden Jubilee--her 50th anniversary as head of the royal family. Americans who have yet to experience the pomp and circumstance of the 291-year-old annual race have a way to join in from afar, now that the prestigious Royal Ascot Collection luxury products have just been introduced to stateside retail shops.You too can don the debonair silk-topped, feathered and flowered hats and logo-emblazoned silk ties. There's even a new line of housewares, fragrances, cigars and teas, and--our favorite--a series of antique-style, leather-bound flasks and carrying cases perfect for Ascot week (June 18 to 22) or a summer picnic. "It's all terribly British," an Ascot spokeswoman says. "And that's just what people love about it" (leather carrying case with shoulder strap and two flasks, $266;