Where can I purchase new spider and spider gears for the model A?

[Willie Krash]

I'd be inclined to look for a whole rear end and change it out. I'm cheap and lazy. Maybe a fool too. Around these parts they pop up and are very reasonable.
Hot rodders will sometimes practically give them away.
You might put in your profile where you live. Model A folks are very generous and like helping out fellow enthusiasts. If I had them I'd give 'em to you, if you were near by....