By Michelle Conlin NEW YORK, Oct 4 (Reuters) - Carly Fiorina has emerged as the Republican candidate of the moment in conservative fundraising circles, drawing the notice of the billionaire Koch brothers and other wealthy donors who could instantly remake her shoestring presidential campaign. Fiorina's show-stealing performance in a Republican presidential debate last month, and her subsequent surge in the polls, has prompted industrialists Charles and David Koch to take a "serious look" at the former Hewlett-Packard chief executive, according to three sources close to the brothers.