Small Engines (Lawn Mowers, etc.): Atlas snowblower Part, atlas snowblower, e bay

Question
I have an Atlas snowblower with a model number A 5220 M, or SC 5220 M, not sure witch one.  I need a worm gear part number 612903.  I really only need half of the worm gear, the one that sits on the auger shaft.  I have been told MTD bought owns this brand now and they have discontinued the part.  Can anyone possible help me out?

Answer
Atlas parts are very difficult if not impossible to find.  We maintain a "bone yard" at our shop but we don't have any Atlas snowblowers...that's how rare they are these days.  It's possible to adapt another gear box but this would require consideralbe time and probably more money than it's worth.
Have you looked on E-bay for a parts donor or tried some local shops in your area to see if they have any old units lying around?
Eric