@erps - That may work.
Of course I'd still love to find the actual socket to fit this nut, but in a pinch, your solution might be what works. I'll try to track one down.
@Sixpoint - Well, I'm not much of a welder. :P I hope it doesn't come down to making a custom part for this, but we'll see...
@QuickMick - Nope, that's not it. Here is the direct link to the photo: http://imgur.com/0paoH.jpg