Hey, I’m a senior in BSN school so perhaps someone still in school can help.
I also face a similar thing, of doing very well, not needing any help, and therefore not being close to a huge amount of teachers. However, I got to know a few teachers through nursing related clubs, the nursing honors program I am in, and just by answering and asking questions in class. Surely there has to be ONE teacher you interacted with often enough? I think to admission boards, being able to get letters of recommendation even after months of being graduated shows that you were somewhat involved and that you stood out. So definitely attempt to find a professor. Choose one from a class that you feel like you demonstrated a lot of learning/growth in, email that professor, and let them know how much you enjoyed their class and how well you did, even if they don’t remember you. This will soften them up and enable them to whip up something.
The longer you wait, the less any of them will recall you!