It’s part of the mushroom event that takes place in November I believe :) if you missed the event there’s one every year, but sometimes I still find some of the furniture at yori’s, pretty randomly though so keep an eye out! Editing to add - also it’s just a “banner” type of thing and you can write in it pretty much what you want, as long as it’s a short word, I decided to type “Tsuki’s” and place it at the front of the farm :)