Place large eggs in single layer in saucepan. Add enough water to cover eggs by 1 inch. Bring to a boil. Immediately remove from heat; cover and let stand 15 minutes. Drain; rinse with cold water. Place eggs in bowl of ice water; let stand 10 minutes. (For extra-large eggs, increase stand time in hot water to 18 minutes. For medium eggs, decrease stand time in hot water to 12 minutes.) Peel eggs; chop.
In medium bowl, combine chopped eggs, onions, carrot, celery and radishes. In small bowl, combine mayonnaise, mustard, milk, salt and pepper; mix well. Add mayonnaise mixture to egg mixture; mix well.
Place 1 lettuce leaf half in each pita bread half. Fill each with egg mixture.