Buy at player stalls in Providence city, or trade with a player at barrels in Providence city.
Buy several and plant some in pots for future use.
You will get more responses from players if you post on the game's discord channel.
This forum will probably not be very active until our developer returns.
Here is the discord link:
https://discord.com/invite/Wd5T3ex ...or:
https://discord.gg/Wd5T3ex