Chatsworth-based Sexy Hair has named American Idol runner-up Katharine McPhee its spokeswoman. McPhee will appear in the company’s ads and promotional materials through 2007, the company said. Michael O’Rourke, Sexy Hair founder, said McPhee will also be involved in some aspects of product development and packaging for the company. McPhee, who is a Sherman Oaks resident, came in second in the 5th season competition of American Idol, narrowly losing to Taylor Hicks.