Hello neighbor! I'm in Chelsea. I get grass-fed beef and buffalo at the Union Sq. Greenmarket. This is the beef vendor:
You can also find it at Whole Foods, and Trader Joe's usually has grass-fed ground beef. Dickinson's Farm Stand in Chelsea Market also has grass-fed beef, as well as lard, duck fat, and other goodies. Pricey though. There's also a NYC Paleo Meet-Up group that I just joined, though I haven't attended any events yet.