shepfl, there are SEVERAL out there to get your harness from. I have used painless,twice, and considered others. You can get them with 12 circuits up to over 20.
I ended up going with Painless again on my panel. I got the 20 circuit one even though 12 would probably do me as I don't get into the gadgetry. Nevertheless, my nephew who volunteered to wire it seemed to favor the Painless, with the Mini Fuse panel, so I went with it. My other "personal" choice was Rebel which will give you a 15% discount if you see the tech tip here on the bolt and call after 5pm. (double check me on that)
Both line is I think they ALL are labeled every 5 or 6 inches and most would probably be fine. I did get the feeling that spending a lot of money would only give me braging rights but not necessarily the best value for my buck. So, as I always say, decide what you want, do the homework then put it in black and white and you'll have your answer.
Good luck. Let us know what YOU decide on and Why. I'm curious!!