Walden Media has come on board to co-finance with Mandate Pictures "Mr. Magorium's Wonder Emporium," starring Natalie Portman, Dustin Hoffman and Jason Bateman. Richard Gladstein and Jim Garavente are producing the film, which marks Zach Helm's directorial debut. Production will begin this month in Toronto. Upcoming Walden films include Carl Hiaasen's "Hoot," Thomas Rockwell's "How to Eat Fried Worms" and the Dakota Fanning starrer "Charlotte's Web." The company also is developing the second installment of "The Chronicles of Narnia."