You will really have to dig deep to find some PS5 plugins and brushes. This is mainly due to the lack of an online community around the time PS5 was mainstream. Back in the dialup days and older when the net was just becomming popular PS7 was the main source of community plugins. The best thing to do is at least upgrade to PS7, where you'll find slightly more goodies for you to play around with.
If I find anything worthy on my travels for 10-12 year old versions of Photoshop I'll link you up on this thread. But an upgrade is very highly recommend