You can buy Shroomberry and Warm Hot Spring Stone, (not a lot, but still!!!)

Erica's Store, requires finishing a small decoration quest to unlock

Only 1 stock of each, and needs a small quest to unlock this store, but still! Super helpful at the early stages of your stalls development
Now I have an urge to search the map looking for similar stores (they probably don't exist :( lol)

Here is the location

https://preview.redd.it/8zdt4pb735ng1.png?width=538&format=png&auto=webp&s=2730f6dc9ea4dc64f43fecc6775e61edc7fc7618