The Powerhouse Science Center is looking for a few good founding partners. The Discovery Museum is trying to recruit private investors who can provide seed money to help build a $50 million "iconic" riverfront science and space museum hoped to rival some of the nation's biggest science museums. The new, expanded museum is being developed to provide adventurous, hands-on science and math education to boost kids' interest in the subjects and to help draw high-tech companies — while launching the kind of serious waterfront development that's been talked about for at least three decades, museum supporters said Tuesday. The four-acre campus would contain a museum built in the long-vacant Pac