Keep that place Wilder's that I mentioned in mind if you ever need any obscure hardware (or anything hardware related) in the future. It's an old family owned place with a service counter in the front. You sit down at the counter and tell them what you need and they pull it from the warehouse.
I went in one time because I needed a huge nut to go on a hydraulic cylinder. It was about 1.75", if I remember correctly, and it was fine thread. I sat down and said "I'm not sure you're going to have what I need, but I figured if I could find it around here anywhere, it would be here." The guy proceeded to tell me that they have anything you need in stock up to an 8" diameter, anything over that has to be special ordered.