The Leaky Cauldron is a fictional pub in the Harry Potter series, serving as the entrance to Diagon Alley. It's a location in the game, not a cheat code location.
To find cheats for the PSP version of Harry Potter Years 1-4, you'll need to search online. Be cautious about websites claiming to offer cheats, as some may contain malware or viruses.
However, it's important to remember that using cheats can take away from the enjoyment of the game and may make the game less challenging.