I think our reel mower guys will need pictures of that mower to be able to identify it, sorlawn. The reference to a plastic gear driving the rear roller sounds like an SB Diplomat (model 430 or 590) but that doesn't lead me to a Morrison sticker.
If you have a Diplomat with a broken or slipping roller drive gear, that is a characteristic fault in those machines, and unfortunately the plastic gear is no longer available.
