Just to report back on this - my early 2017 Model S doesn't have the wiring either and the technician also checked with Tesla who said that if if didn't come with factory wiring harness then there won't be one so you need to custom create it as others have said... Tesla also don't have a specific wiring harness for it so feels a bit weird since if you actually damage it, there's no way to replace it other than to fix it.
These are the sun visors for the black headliner for UK:
ASY, SUN VISOR LEFT HAND, ULS BLK, NO LABEL (1143824-46- C)
ASY, SUN VISOR RH, ULS BLK, NO LABEL (1143825-46-B)