Hej Artur
Years ago I have the same problem with electrikc cables for an EW.
I whent to a footwear shop and purchase some round weaven shoelace in different size and lenght.
You can buy them in black,- made by cotton.
It is easy to put an modern electrik cable inside this shoelace,- and then tighten it up.
You will then have a cable with the same outside looks as and old cotton cable.
It is possible to put several cables in the same shoelace,- and in this way made a complete electrik wire system for the bike.
Good luck and regards from Edin DK