The file you are looking for, PSVUPDAT.PUP, is the official system software update file for the PlayStation Vita. While "patched" or modified versions of firmware files (like those used for downgrading to 3.60 or 3.65) are often discussed in the homebrew community, the standard way to obtain the base firmware for tools like the Vita3K emulator is directly from PlayStation's servers. How to Create the Update Structure
Disclaimer: Modifying your PlayStation Vita may void your warranty and violate Sony’s Terms of Service. This article is for educational purposes only. Always backup your data before modifying system software. psvupdatpup download patched
Conclusion
Official Source: Sony’s servers host these files. However, they only provide the latest unpatched firmware (currently 3.74 or 3.75), which closes many exploits. The file you are looking for, PSVUPDAT