I assume by “MJ cell shader” from ePSXe, they are referring to my old Pete’s OGL2 shader. If so, I did a port to Retroarch about maybe a year ago (under the “cel” folder in the shaders directory).
There should be both single-pass and multi-pass versions, with the multi-pass one adding some blurring to the outlines to try and make them stand out more in higher internal resolutions.
I know there was an issue with running one of the versions of them on my Shield (error loading), but I never got around to figuring out why.
Edit: Just looked at the RAR uploaded and that looks like those are the ones guest did for Pete’s OLG2. So, not the same as what I ported.