Atik383 optical window to buy?

[jolo]

Hello everyone!
Just found out on my 383 optical window glass the surface there is a smudge that cannot be removed using standard cleaning methods. Most probably the protective surface is damaged there. It is actually nothing that flat frame cannot deal with, but just wondering if it is possible to buy optical window glass for Atik 383 separately to replace it by myself? Or do I need to send the camera to the service?

Clear skies!