I'm out of stimulants and 8 would like to know where to buy them in bulk
Honestly, I've just periodically bought them in stores whenever they pop up. It's not rare. Like 3 here and 4 there. They appear on the tables in stores. Just honestly spend the time to buy them that way, dude. There is no bulk option for stimulants that I have seen in over 60 hours of playing. The game kinda puts you in a speedrun mindset and it doesn't need to be that way.
idk if anyone will see this but hopefully it helps:
To bulk buy stimulant you must progress the events with Adrianna (a dwarf girl) until you can access the underground secret dwarf base, go left(ish)-down of the main hall and take the room you see first off the right of the underground where you will find a blacksmith area, the dwarf at the anvil will offer stimulant as well as other useful items like coal, iron bars and mithril bars :)
Here's the link for Adrianna's events: Adrianna - Renryuu Wiki (miraheze.org)