Search for "Mortal Kombat Unchained MKX Mod ISO" or "Mortal Kombat X PS Vita compressed". Avoid sites with pop-up ads and malware warnings.
The mobile version of MKX is a card-based collector fighter, not a traditional fighting game. For arcade-style action, MK11 on Switch is the best portable official option. Search for "Mortal Kombat Unchained MKX Mod ISO"
Since there is no native PSP ISO of MKX, most files labeled as such fall into one of these categories: Search for "Mortal Kombat Unchained MKX Mod ISO"