What is a substitute for galliano in a Harvey wallbanger coctail?

If you need a substitute for Galliano in a Harvey Wallbanger cocktail, you can use vanilla vodka mixed with a splash of anise-flavored liqueur, such as Sambuca or Absinthe, to mimic the herbal and sweet flavor profile. Alternatively, you could use a combination of vanilla syrup and a drop of orange bitters to achieve a similar taste without the specific liqueur. Adjust the proportions to suit your palate while maintaining the cocktail's balance.