Damn, my nearest restroom seems to be about 6600 km away.

If you decide to go global, it's easy to get locations (and sometimes other data, like wheelchair access or even opening hours) from OSM:

- tag: https://wiki.openstreetmap.org/wiki/Tag:amenity=toilets

- example query with Overpass API: http://overpass-turbo.eu/?template=key-value&key=amenity&val...

But this approach (all data in a single huge array) could be pretty slow with a lot of restrooms: https://restroomfinder.co/data.js