I'm in your same position, and in MY opinion, what you have is treasure, not trash.
A little bit of balance for the discussion - many people here on the forum are collectors, and many people either own their own appliance repair businesses, work for one, or know someone who does, giving them a different perspective on parts availability. Or, they have the space and connections to acquire and salvage parts machines to assemble the best of the best into their own machines, but you have to play the lottery that the used machine you buy for parts is in better shape than what you have now. All of that is not always available to, or practical for, the rest of us.
New transmissions of this type have been NLA (no-longer available) for a very long time now. Replacement agitator shafts from Maytag (which used to come as a pre-made assembly with the top half of the transmission case and the small gear) have also been NLA for a very long time. Third-party (non-Maytag) substitute agitator shafts went into production when Maytag stopped, but those have ALSO been NLA for a long time. And there have been very few parts showing up on eBay or the like lately.
You can try asking around at your local Mom & Pop appliance repair shops, but every single one I've talked to said they have zero spares due to the age of the machines. It's worth a try, but don't be surprised if you come up empty.
I feel relatively confident saying all this, because I've been searching for months, and if these parts had been available, I would have bought them myself.
We have a transmission apart from an A308, that has an agitator shaft in much worse shape than yours. Our plan is to restore and use it - following the procedure of building it up with a small amount of JB-Weld to fill the pits, and then polishing it smooth to maximize the life of the seals. Other than possibly a shorter life on the $50 seal, I don't see what you have to loose by trying with what you have, and after taking the machine apart this far, you certainly seem plenty capable of the filling/smoothing job that others have done!
Good luck!