Since the PSP and Vita stores have shut down, you cannot purchase Tag Force Special digitally anymore. Physical copies exist (Japan-only UMD for PSP), but they are rare and expensive ($80–150 USD). Here are legal alternatives:

Stick to well-established, community-vetted ROM archiving websites. Avoid obscure, shady blogs that require you to click through multiple suspicious pop-up ads.

The base game was only released in Japanese. To get the best experience, search for a "clean" or untampered Japanese ISO. You will manually apply the translation patch later to ensure no data corruption occurs. How to Apply the English Translation Patch