All apartments in NYC have floorplans. It's just depends whether the agent uploaded it to their website or not :) If you are working with an agent to help you find your next home, they should be able to pull up any apartments floorplan for you.
My friend Doug Heddings from Prudential Douglas Elliman and author of True Gotham, has an excellent video series about NYC's mythical square footage......Please see the link below....
Social Media Guru at Trulia
IMO, floorplans w/true measurements, an accurate and detailed property description, quality photos (and even a video walk-through) should be available "on demand" to all prospective buyers. Why not?
BTW: Some agents do provide this level of service. My Douglas Elliman colleagues send me their NYC listings and most do these things and more.