I googled the grease seal number you mentioned and I did find some options online but when I looked up the size it wasn't one that we carry a suitable replacement for.
For a coupler solution though you could use the Dexter part # T1607500 which you'd want to weld to the top of your trailer frame. It was not designed to fit over a frame channel so your width being wider than usual wouldn't be a factor. view full answer...