There is no official UMD or digital version of Rumble Racing in the PSP library .
While the PSP can emulate PlayStation 1 games natively, it does not have the processing power to emulate PlayStation 2 games like Rumble Racing. Download Rumble Racing Psp
You can play the original PS2 version using the AetherSX2 emulator on Android devices. You will need a legal backup (ISO file) of your Rumble Racing disc. There is no official UMD or digital version