Anyone know how to borrow a Gramercy Park key for a day?

My girlfriend and I have lived in the Gramercy Park neighborhood for a few years now and have always loved it, but we’ve never actually been inside the park itself. I’m planning to propose to her soon, and given how many big milestones in our relationship have happened in this neighborhood, it would mean a lot to do it inside the park.

So… does anyone know of a way to borrow or rent a key for a day?

Thanks in advance!