Zero Point Egg Salad Sandwich

Eggs: 4 large (hard-boiled and peeled)
Non-fat Greek yogurt: 1/4 cup (as a mayo substitute)
Dijon mustard: 1 teaspoon
Celery: 1 stalk (finely chopped)
Red onion: 1-2 tablespoons (finely chopped, optional)
Fresh herbs: such as chives, dill, or parsley (finely chopped, optional)
Salt and pepper: to taste
Lettuce leaves: 2-4 (for extra crunch)
Tomato slices: optional
Zero Point bread alternative: lettuce wraps, or a small serving of whole grain bread (check for low or zero point options)