There is the Native American Museum at Garvies Point in Glen Cove. I have not seen their collections in many years.
You have to remember that Long Island's Native population was probably 3/4s decimated by 1720. Sadly for many reasons, but mostly from smallpox epidemics. During the early contact period, the Native Americans would fashion arrowheads from copper kettles. Then Europeans started to make and trade the basic triangular points like you found. The hole was not only used to haft the point to the shift, it was also handy to string many together for transport. It probably wasn't long before they were able to trade for black powder firearms, making bows and arrows obsolete. They are rare in the sense that they had a limited period of usage. More examples are turning up from metal detectorists. They are turning up at dig sites in upper NYS.