Some counties in New York state have tallied the number of write-in votes. The returns for those counties suggest approximately 1% of voters cast a write-in vote for president. If that holds for the entire state, there will probably be 80,000 write-ins when all results are tallied.
Among the five boroughs of New York city, Manhattan (New York County) is the only one with a write-in tally so far. The percentage there is 1.9% of the total, or 11,421 write-ins. This news story has the presidential results by county, but obviously many counties have not finished the write-in tally because they show zero write-ins.