I use the woven split loom from Alex Tech that you can find from the link
@HumanPerson gave above. Its sold in a boatload of different widths.
Here's something else you can do: Go to the local big orange hardware store and get yourself some vinyl pool tubing. the clear stuff with the cross-woven ribbing. Wide variety of diameters so pick one of your choice. Cut an appropriate length and slit it lengthwise. Put wiring inside and use velcro One Wrap ties to close it back up. You now have many wires/cables bundled and protected inside a tough outer casing. (you could do the same thing with 1" lengths placed at intervals and gorilla taped).
I've done that using 3/4" ID silicone tubing I had on hand. Its black and blends in as a result, but buying that for this task is a pretty pricey. A wrap of black gorilla tape over the tubing would handle the blending thing.