Shouldn't that be a rebuildable part? Don't they normally just clean em up, replace the brushes and check the selonoid?
Pull it off and take it to an Alternator/Starter tech.
You should be able to find plenty of them in your local Yellow Pages.
If they can't rebuild it, they should be able to find you an exact match.
I would not think that you would be down for more than a couple of days or so.
Courtney is My Hero
If a man is to be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most - E.B. White