Collective Brands, parent company of Sperry Top-Sider, Keds, Pro-Keds, Stride Rite and Airwalk, Saucony, has reportedly hired an investment bank, Perella Weinberg, to look for potential buyers for its whole business, which includes the loss-making Payless ShoeSource chain of shoe shops, or parts of it. The company indicated last August, after the departure of Matt Rubel as president and chief executive, that it was conducting a review of strategic and financial alternatives through Perella and Kurt Salmon Associates. The new phase of the exploration appears to have been triggered by the 73 percent drop in net income that it suffered in the third quarter and by a debt load of more than $600 million.