Couldn't give you a direct link as I haven't saved any of those threads.
I recall one or more being on a certain 3ds iso site (<_< .. >_> ) which can't be linked, so you'd have to google.
Pretty sure i've seen at least one person offer a service here, usually if someone goes with this option, they want to buy from someone with a high post count; thinking that person would be more reliable / legit than someone with a lower post count.
If buying a header is the route you want to take, i'd just look around a bit. Shouldn't be too hard to find someone, just know that you're taking a chance / trusting the person you'll buy from will only sell that header to you.