Here is a list of Mikvahs within 4 miles that are an easy drive or subway ride:
The Mikvah on Carroll - 1508 Carroll St https://themikvah.info/
Park Slope Mikvah - 292 15th St https://parkslopemikvah.com/
The Jacques and Hanna Schwalbe Mikvah- 419 E 77th St, Upper East Side
www.chabaduppereastsideThe-Jacques-and-Hanna-Schwalbe-Mikvah
Chabad Brooklyn Heights Mikvah- 117 Remsen St
https://www.heightschabad.com/templates/articlecco_cdo/aid/1816595/jewish/Mikvah.htm