Talk about a public service.  The Downtown Alliance made a list of the public bathrooms open south of Murray, their catchment area:
—Teardrop Park (inside the Solaire Building)
—Wagner Park (located north of Historic Battery Park, off Battery Place)
—Staten Island Ferry Terminal (4 Whitehall Street)
—Pier 11 / Wall St. Ferry Terminal (South Street)
—The Battery Comfort Station (Battery Place and Washington Street)
—The Battery Gardens (Battery Park Underpass at South Street)
—Brookfield Place (230 Vesey Street)
(The Oculus is still closed)

I am adding these north of Murray:
—Pier 25 (at N. Moore in Hudson River Park)
—Washington Market Park
—Pier 45 (at 10th in Hudson River Park)

The alliance offers these friendly reminders: keep your mask on during your public restroom outings, put the lid down when finished and wash your hands thoroughly. That means lather with soap for 20 seconds and rinse with water, per the CDC. And if you happened to use your cell phone during this time (ugh), please remember to wash that thing too.