Just about any 8" or 10" chuck out there will work. Your problem is going to be, is finding a A-1 or A-2 back plate. I saw your post over on PM and John O mentioned it was a A-6" nose. With that in mind, you could take a D1-6" adapter plate, pull the pins, and drill/C'Bore holes to match up with the spindle nose tapped holes. There are not very many NOS chucks out there with a A series back to them. MAybe a few used ones that would work. If you find one, it's more than likely worn out. Be nice to find a old W & S 3-jaw chuck in good shape. They are hard to come by.
Ken