I live about four blocks away from Manhattan's Koreatown in the "30s," there are a few spas listed in the following link, a few years old:
https://theculturetrip.com/north-america/usa/new-york/new-york-city/articles/the-best-korean-spas-in-new-york-city/
But if you're looking for spas with communal areas, wouldn't these be likely to face (temporary but rather long-term) closure due to Covid?