My 1310-1510-1710 Repair Manual does not show any accessories, unfortunately, just the basic tractor. Although one picture leads me to believe that it may have been originally a two lever setup. I'll have a look at the WEB sites you suggested.
The part is simple enough, I may take it to a local machinist and have him turn a replacement, maybe two. Removing the piece which is broken off in the lever assembly will take more work, but no insurmountable. Looking at the broken surface, it has been cracked ~1/3 way through for a long time, there is rust and dirt.
Thanks for the assistance.
John