To get you started
American Restroom Association
World Toilet Organization
Photo source https://www.worldtoilet.org/rainbow-school-toilet/
The public toilets reopening in Cambridge city centre this weekend:
Carry change for toilets, which often have turnstiles at the entrances. Public WCs of AMAV, the Venice sanitation authority, charge a mind-boggling €1,50 unless you have the Venice Connected pass. Larger museums (such as the Doge’s Palace) have attended restrooms with posted fees. In other museums and galleries, toilets are often free.
The Portland Loo