What do Elle McPherson, The Backstreet Boys and David Copperfield have in common? They all drink milk with their cookies, and have autographed their GOT MILK? Milk Mustache ads to benefit Big Brothers Big Sisters of America. The California Milk Processor Board (CMPB), creators of the famed GOT MILK? advertising campaign, today announced plans to conduct a charity sale of exclusive GOT MILK? memorabilia on eBay, the world's largest on-line trading community. GOT MILK? items available for bid include one-of-a-kind celebrity autographed ads, TV commercials never before available to the public, the rare collector GOT MILK? Barbie and out-of-production toys. The bidding frenzy takes place at