Walmart has the Huffy Girls' 10" Minnie Bike in White, model no. 57472 (pictured), or the Huffy Boys' 10" Disney Mickey Bike, model no. 57462, for $29 plus $4.97 for shipping. (Site-to-Store pickup is also available.) That's at least $28 below the lowest total price we could find for either bike elsewhere. These single-speed bicycles both feature training wheels, foam tires, and hi-rise handlebars.
Order by December 19 to guarantee delivery before Christmas.