I am back from NYC. I ended up buying a Spyderco Grasshopper from their "Slipit" line. It's a very small non-locking knife. While it has the Spydie Hole it cannot be opened one handed no matter how hard one tries; even if I turned out to be wrong about that it's still NYC legal when kept in a pocket.

The one interaction with NYPD was brief and professional. They came swiftly when I called 911 to report an emotionally disturbed person harassing and scaring people in my mother's neighborhood; after asking me what the EDP had done I was on my way. They were, a family member who has reason to know explained, waiting for a Sergeant with a Taser (in case gentler methods failed) before trying to get him some help.

The knife came with a wicked edge from the factory and was used almost constantly during the brief trip. For small cutting jobs it works admirably. I'm glad I bought it.