I just received in a Boston Electric Pencil Sharpener - Model 19. My testing shows that the large gear for the Model 18 is a suitable replacement for the model 19! If you have a model 19 with a broken large gear, the replacement that I have available will work. This is a repro of an original part but made from more durable material.
I am now posting these on ebay with a set price, no waiting on bids or auction end time. The auction on the previous post ended with no takers but this item has been listed again.
Note: correction has been made to this post - the Model 18 part can be used to repair a Model 19 sharpener. The replacement for the Model 17 is very different and NOT replacable by this part. My ebay listings also mention which models are compatible with the item being listed. Sorry for any confusion!