Probably the biggest name in this space is Painless, but they tend to be on the pricey side, and I always wonder to what degree they can deal with the nuanced variations as our jeeps evolved. But they make a lot of money so I assume they probably have all that worked out.
Used is always an option and will save you a chunk of money. However I would expect that unless they say it's been reconditioned, there is a strong possibility you will find some wires in need of repair within the harness. But that's good, you can inspect the whole thing, put a test light on each wire, etc and feel really good about the harness when you install it.
But maybe a better question to ask here is "what problem are you trying to solve?" A new harness is a hassle if all you really need to do is repair a few wires.