unfortunately your going to have a problem looking for boots on LI, sno haus is a great shop, cool pplz great customer service and decent board and binding selection but a VERY small boot selection, Ski stop has a bit of larger boot selection but not many brands I think only k2 flow and burton if I remember. Sundown the last time I was in there only had about 6 boots for men and I think 5 of them were burton (this one I could be wrong about) I dont know what it is but im not diggin this shop so much. Theres a few shops in the city you might have some more luck at google snowboard shops in NY. hope this helps. if you have a speific boot in mind hit them up to see if they have it if not might as well take a day n hit all them up n try as many on as possible just to make sure you find the right boot. the wrong boot will KILL your boarding season.
I got my boots at Sundown on 110 in Farmingdale. They had a decent selection and the guys there really know their stuff. But yea, there aren't really Too many shops with BIG selections due to the fact that we don't have anything to board here to it's not worth it for them have a big inventory.