In a small bowl, combine the sour cream, buttermilk, the cider vinegar, and the dip mix. Whisk until the mixture is smooth. Fold in the garlic and ¼ cup of green onion; set aside. Core and cut the head of lettuce into 4 equal wedges. Place each wedge of lettuce onto four plates. Drizzle approximately ¼ of the salad dressing over each wedge. Top each wedge with ¼ of the remaining green onions, ¼ of the diced tomato, and 1 teaspoon of bacon bits.