The short answer is . There is no official version of The Last of Us for the PlayStation Portable (PSP).
While the original game won't run on PPSSPP, fans have created some legitimate ways to experience the world on mobile or handheld devices: How to Play The Last of Us on Mobile (Android) | Full Guide
: A lightweight, third-party fangame on Uptodown for Android that tries to mimic the game's atmosphere but is not the full original title.
But here is the hard truth: Consequently, there is no official, playable, or legitimate “The Last of Us PPSSPP ISO” in existence.
Unfortunately, . The game was never developed or published for the PSP, and its system requirements are far beyond the PSP's capabilities.