I noticed a new baby villager today. It was the only new one in the village. Once it was grown up I saw that it was a cartographer and began trading with it. I sold him paper and compasses until he sold out. Closing the trade window and opening it again did not show new trades available (20% chance).

I then left the chunk and returned and he was selling more where normally when you buy out a villager they remember forever. I kept doing this. Sometimes when the villager didn't have trades I would go craft something and come back to him and he'd have trades. But most of the time I had to leave the chunk and come back. He gave me 230 emeralds in total before he wouldn't trade those items anymore.

I cannot verify if I've ever traded with any other cartographers or baby villagers that grew up.