If you'd like to try out the fan-made mods, I can help you find: The that add Street Fighter characters
A guide on on the PPSSPP emulator Information on how to get the Vita version running today Street Fighter X Tekken Psp Iso Download
When searching for ISO downloads, be extremely careful. Many sites promising "highly compressed" or "rare" ISOs of games that were never released (like SFxT on PSP) often contain malware or broken files. Always stick to reputable community forums if you are looking for fan-made mods. If you'd like to try out the fan-made