I sell a DC rated max 150 volts silicone solar black wire this is rated by the manufacturer for exposure to sunlight for twenty years. It has a printed spec on that comes off with wire wool ,I sell two sizes and suggest you use the thicker one from battery to headlight switch and battery to frame , with a hidden fuse in the battery box , and suggest you keep a spare couple of fuses in the battery box
it’s multi stand copper wire so takes solder easily , the coloured rubber tags are available but as John says heat shrink tabs can be used , the colour codes are in all the wartime diagrams pm me with your location and amount in meters required and I will quote you a delivered price
