Connect your PSP to your computer via USB. Navigate to the root of your Memory Stick. If you have CFW installed, you will see a folder named ISO (capital letters). If not, create one.
Due to copyright restrictions, I cannot provide a direct download. However, search for or "Reddit r/PSP Plants vs Zombies Megathread" – these communities regularly update the links every month. plants vs zombies psp iso updated
However, the keyword persists for two very specific reasons: Connect your PSP to your computer via USB