"IF" you know how to solder and are good at it, [or willing to learn] its really not hard to make a really top quality cable of almost any gauge you want. it just requires a bit of care and the willingness to start over if its not perfect, but once you have a soldered, heat shrinked cable the right length it will last a very long time. I've done most of my own wiring for many years [bad starter wire on 79 sportster started that skill set] no failures of any kind in the last ten years on bikes, cars, dozers, etc etc. patience and not skipping any steps are the key. never use wire that is not perfectly shiny when you strip it - always use first class new shiny copper fittings - no copper plated stuff, lead plated steel parts are ok if you don't overheat the parts and use good hardware. dielectric grease reduces contact corrosion issues.
i always up size the wire - labor is the same and it only costs a few cents to use a very good wire compared to a crappy wire.