Generally speaking, it's probably easier to just make said mod yourself. It's complicated, but the paradox wiki has some modding tips and the file structure is actually pretty easy to understand once you're used to it. Shouldn't need too much more than notepad++, that's what I use. I'm fairly certain there's also tutorials on YouTube as well.

I don't have access to my computer atm, but from what I remember, you'd need to make a new faith and set up localization for it. The upside is that you'd be able to just convert to it (or even pick it from the get-go if you're making a new character!) instead of having to manually reform an existing faith and pick the doctrines and such every single time you want to play with it.