Motorcycle Parking in NYC
When I used to work in Midtown I parked both my car and when the weather was good my bike at a biker friendly garage located on West 44th street between 9th & 10th Avenue. About $12 for the day. Not sure about overnight. But it's inside parking and there is an actual motorcycle designated area that you put/park your bike in yourself. Think the managers name was Max. It is also a Budget Rent a Car dealer so there is always someone there watching the cars and motorcycles.
I think that's pretty close to where you need to be. When is your bicycle event? I'm off for a few days so could find out more when I go back to work next week.