Start with a zip tire, your wires (this is usually done in the car), and some small diameter tubing or hose. For the hose the best thing to use is silicon hose, and you can get it in a ton of colors for better looks.

Cut the hose into small secions, about 10mm or 1/4 inch. You will need 1 piece between each wire, so 4 wires takes 3 sections of hose.

Slide all 3 hose pieces onto the zip tire.

Starting at one side feed the zip tie arround the wire then back through the hose section.

Then go over the next wire and through the next hose section.

When you are done you get all 4 wires held apart from each other, but also nicely bundled together. Smaller hose sections will allow the wires to be closer together, I used too large pieces in this case and the wires are too far apart.