Go to car-part.com always alot of used trannys there for our MX's........ but just remember that just because they have some dirt cheap ones on there, doesn't always mean it's a good deal for you in the long run.
If you fall, then get back up........Luck favors the prepared
and now I need one too, i'm new to the forum, just got my MX 6 months ago, love the car, but im into replacing a lot of parts... really sinking a lot of money into it, currently on the agenda windshield and tranny