It's definitely annoying to find, but I usually get it in Korea Town at Hanahreum Asian Mart on 32nd(?) a couple of blocks east of Penn Station. I actually had no idea what it was called, but managed to find it on Google Street View.
Thank you! I was over there today and (though it was hard to find because why would the tofu be in a box next to a cooler of ice near produce?), I was able to stock up for the first time in way too long.