Most anything when you program in the right Pavlovian triggers. Essential / scent oils make some of the best sensory triggers for a trained somatic response because they're so varied and you can usually pick a super specific one so you're less likely to trigger it randomly in everyday life.

Literally just meditate or do something low energy but flow state where your heart rate is low while running it through a diffuser. Do that at least 3 times a week, but ideally daily for a few weeks. Then you can start carrying some saturated swabs in a small sealed container and just whip them out and sniff them when you need to calm down a little. You do have to make sure you keep meditating / chilling to the scent more than you use it for distressing situations because otherwise it becomes programmed more to the distress.