Is there any way I can still fight PLUTO?

i just spent like 2 weeks on my hikikomori file and i just started trying to get all the foe facts but i missed the fight, im willing to resort to cheating is there any way i can still get it? (if there are any mods that allow me to do so with getting the steam achievement that would also be nice) i really dont want to start a new file especially after i finally beat perfectheart.