Those earpads are not compatible with the Audio-Technica ATH-M50x. It looks like they where designed specifically for turtle beach headsets.
However, these earpads are very similar to the ones on that headset: https://www.amazon.com/dp/B00ZGFVEUE/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B00ZGFVEUE&pd_rd_wg=i6sbt&pd_rd_r=D5BJRNVWA381CQWWSRTH&pd_rd_w=eafWZ
You will need to visit the amazon website of your country and search for those.
Hope this helps!