Drugstore chain Walgreen will become the latest big employer to send its workers shopping for their health insurance instead of providing a few choices for them. The Deerfield, Ill., company says it will start giving workers a contribution toward the cost of coverage and then send them to a private health insurance exchange where they will pick from as many as 25 plans. Employers normally pay most of the coverage cost, and Walgreen Co.'s contribution won't change. It says the move offers more choices for workers and will make them better health insurance consumers, which can help control costs. Employers have struggled for years with health care costs that climb faster than inflation. Sears Holdings Corp. is among the companies that have already shifted to this relatively new approach.