It's possible you're thinking of the "Revival Herb" item itself. This item can be found in various places in the game, including:
* Purchased from shops: Some shops in the game, such as the one in Jubilife City, sell Revival Herbs.
* Found in the wild: Revival Herbs can occasionally be found growing in the wild, usually in grassy areas.
* Received as a reward: You can sometimes receive Revival Herbs as rewards for completing certain tasks or battles.
If you're looking for a specific location, please let me know what item or shop you're looking for and I can try to help.