Not knowing the condition of your harness - but having built some K bike harnesses myself - I'd suggest taking all the tape off the existing harness and assessing the actual condition of it. If it's a case of hacked wires - you might consider doing a professional splice (with the correct soldering of the connections and shrink wrapping) to repair them. Repairing the harness will be much easier than reproducing it, and you'll have all the correct wire colors - trying to find purple with a gray pinstripe wire will be almost impossible.. (just an example..) Troubleshooting down the road with a home-made harness where the colors don't match the diagrams will be quite frustrating.
I started building a wiring harness table/board yesterday and will finish it today. Then I'll pin the OEM harness to it and start splitting and labeling it.
This process will teach me how to read and understand the wiring schematics in the manual.
Or you might consider putting feelers out for a good used one. If you're patient these sort of things sometimes show up very cheap (I picked up a spare R1200R harness - complete and with 2 O2 sensors for $75 off ebay..) When I had a bad harness on my K75S (it caught fire.. not fun, too many un-fused wires in too tight a package) - someone on the IBMWR sent me a replacement, and refused to take any money for it.
Just a thought - there are sometimes other ways to skin a feline..