Q. Where can I buy clivia plants in the New York City area?
PHS is located in Philadelphia, so we are not really the ones to ask about plant sources in the NYC area. A very good mail order and online source is Logee's Greenhouses (and they have a retail store, in Connecticut).
I suggest you contact a plant specialist at the New York Botanical Garden. That specialist will tell you good sources for Clivia in the NYC area.