Not to be rude or factious - "get good".
Start by googling words and phrasing such as:
"Philips Fidelio X2HR replacement leather ear pads".
I found the following link
https://www.amazon.com/Fidelio-x2-Earpads-Headphone-Accessories/s?k=Fidelio+x2&rh=n:13880181
I also found a few other similar links.
"Dirty", "Comfortable", "compatible", etc. are subjective for the most part.
So the solution is for you to start looking, learn, and continue searching for earpads that meet your requirements.
Unfortunately, any product (earpad) that seems to meet your requirements may not suit.
Overall the best option , in my mind anyway, is to go "hands on" with as many earpads and even headsets as you can manage to look at and try in stores, via family members, and via friends.
Tough with the current pandemic.
That all said: "rather dirty". I would google "leather cleaning products".
Leather tends to discolor with age but it can be cleaned.