[Andrew]

They come up on ebay, or one of the local clubs might have one for rent/borrow. A fair number of people have made the tool by cutting a socket to fit.

Andrew

 

[Andrew]

In fact, there's one on ebay now, with one broken tang: 120148598111

I think this one is for 2000s. There is one size for 1300-1750 axles and a larger one for 2000 axles.

Andrew

 

[Andrew]

Here's a link to a guy who made a 2000 one. Just to clarify, Alfa did make factory tools for both sizes; they're just getting harder to find, particularly the early, small type.

http://www.geocities.com/motorcity/downs/3837/ringtool.html

Andrew