As Sharon Spangler walked door to door in commercial districts to drum up interest in Reno's first Buy Local Marketplace, she discovered an unexpected problem.Many of the city's smallest retailers, the ones that might gain most from a buy-local event, are so strapped for resources that they can't simultaneously keep their stores open while they staff a booth at the marketplace.But enough of them have found a solution often, neighboring shops are combining forces for the day that the city government expects between 80 and 100 businesses to participate in the marketplace on Nov. 3, says Spangler, a community relations …