In the 2001 Harry Potter and the Sorcerer's Stone game (PC/PS1/PS2/GameCube/GBA), potion ingredients are scattered across Hogwarts—classrooms, corridors, the Forbidden Forest, and hidden chests. Use Flipendo or Revelio (wand scan) to reveal concealed items.
Explore thoroughly, scan often, and you'll stock your cauldron in no time.