toddler using breasts for comfort

Hi my lo is 18months old and since stopping breasr feeding nearly 10months ago is using mine, her nursery staff and grandmothers boobs for a source of comfort! How can i stop this? She has a dummy when she sleeps which we also tryin to stop her using and i say no to her when ahe touches them,but she keeps going back. Im due to have another baby in 2months so need to get her out of habit as i want to breastfeed new baby. Any suggestions on what she can use instead? It seems to be when we cuddling and shes tired. Many thanks. Anita