By Bass Drum "skins" I trust you mean the playing surfaces? I haven't looked into having those made up... however seeing as the SDX BD is essentially an SDS9 Pad with a great playing surface, I was always of the opinion that one might "paint" the black playing surface with a rubber based grey paint that would adhere to the surface.. but I never tried that so I don't know how it would hold up or look....
To be clear, it's the Bass Drum SHELLS that I was inquiring about... not the surfaces.
Cheers
A