I don't think there are any psilocybin "storefronts" in Halifax yet but some of the non-NSLC dispensaries are known to sell shrooms and derived products. I also frequently see ads on social media for mail-order shroom dispensaries. I wouldn't be surprised if there were 1 or more low-key but blatant shroom dispensaries elsewhere in the province at this point in places like Wolfville, Shubenacadie, or Cape Breton. But as far as I know there are none that have garnered attention.
I've also seen businesses in BC and/or ON that openly advertise coca leaf and I think even DMT/ayahuasca, although not in NS.
Anecdotally it seems like mushrooms are fairly easy to grow at home (or wherever) - the amount of space/effort required is much lower than with cannabis for example (or even tomatoes) and I can't see them needing any more than a negligible amount of light or water. They're generally not treated as a "serious" drug by the police or courts here (I don't think I've ever heard of anyone going to jail over possession or even trafficking of shrooms unless it was on top of a bunch of other charges) and so a lot of people just casually grow them themselves.
Because of that widespread DIY factor, they don't really generate revenue for organized crime or involve international smuggling operations and have a low risk for cross-contamination, and they pose relatively few health risks and don't tend to be associated with violent behaviour - they are very low on the list of drugs that authorities here "care about" in any meaningful way. Mostly they care about cocaine, which is the polar opposite in all of those ways. There seems to be some interest here in clinical/prescription use of psilocybin but I think ketamine is a few years further along that path at this point (available as an "option" to a lot of patients, sometimes covered by insurance/sometimes not, it seems there are a lot of clinical trials happening here).
Fun fact:
Psilocybe semilanceata grow wild on the Halifax Citadel and in several other local parks.