You can try talking to the dealer, i don't have high hopes but you can try.Only the 753 with serial #512211005 thru 512211999 used the same axle(6706427) as the 773.
S150, S160, S175, S185 and S205 models all used the same 6706427 axle.
It's possible that a machine shop can machine a new keyway on the opposite side. This will only work of the taper is still good, if it's damaged, you will need a new hub and shaft