Why do you think you broke the bearing ? I don't have an exploded view on hand but the bearing is "far" behind the steering wheel hub. Maybe I'm wrong but IIRC the hub presses the spacer tube that presses the spring who maintains the bearing where it must be. I can't see how you can break this bearing trying to take steering wheel off.
If nobody has the exploded view on hand I will post it tomorrow.
I guess your best bet is to get the broken one out - most bearings have an international reference number (DIN?) on them that bearing shops can match up for you.
It is such a rare part to break, I doubt you will find that listed from one of the usual alfa parts suppliers!