you are looking for 550 paracord.
this will do all of your PSU 18ga wires.
with some pateince can do a 4-wire PWM fan, 3-wire easy.
i get mine from a couple of sources here in the states. even our local hardware
stores carry paracord.
once you find it, make sure you buy enough and then some. sometimes the dye
lot can be different and the "color" maybe brighter or duller on the next purchase.
generally, a single color on just a 24-pin @ 550mm long is 44feet.
550mm times 24 equals 13200mm.
13200 divided by 24.5 equals 520inches
520 divided by 12 equals 44feet
then you still have your molex, PCIe and what not.. i usually buy a 100feet for $10USD