Finding a Part for Memorex MVD4540

Question

I have a Memorex MVD4540. There is a small plastic wheel inside that has a broken tooth that prevents proper operation of DVD player. All I am trying to do is find out where I can order or pick up this part. I'm in Ontario Canada near Michigan border. I'm not sure where the manual is so don't know where to phone. Web search is producing all kinds of sites except what I'm looking for.