The RW software (Read-Write tool) is essential for gaining write access to the protected sa0: system partition. Install the latest version of the RW tool on your hacked PSVita.
Developers host verified font packages on GitHub. A search for psvita-font-full will lead you to repositories like "TheOfficialFloW" or "SKGleba" test packs. Look for a file named font_pack_full.vpk or a folder containing ltf and pvf files. download font package psvita full