I have searched for replacement bearings without much luck myself. Due to the limited space allowed and thin walls of the tube, I have had to polish the race cups and purchase new balls. Ball Bearings are cheap!
The later ones did come with two nuts and a special slim spanner needs to be fabricated for their removal. 1 5/16″ A/F is a little too thick and a wee bit needs to be shaved off for the nuts removal.
You will need access for a lathe for polishing the bearing races. A smooth finnish here helps to remove future friction. The cause of the problem is the heat from the exhaust manifolds/headers causing the grease to melt and drip dry. A good High temperature seal is required for a proper repair. Anybody found a good seal they modified for keeping the grease in?