"Sanctuary for smokers" is a good alternative to "haven for smokers." Other synonyms include "refuge for smokers," "retreat for smokers," and "oasis for smokers." These words capture the same idea of a place where smokers can congregate and smoke without judgment or interruption. However, it's worth noting that as attitudes towards smoking change, these terms may become less frequently used or may be repurposed to describe other places or experiences. As such, it's important to stay aware of changes in language and how people talk about smoking and related activities.