Trans woman Teagan Widmer created a free app designed especially to help trans people find accessible safe public toilet accomodations. You can access several different public toilet finder apps.

http://www.advocate.com/politics/transgender/2014/02/07/trans-woman-releases-bathroom-finder-app-refuge-restrooms

You ought to have this. Need it just one time and you will be glad someone told you sbout it. Bathroom Finder on Google Playstore accesses public toilets worldwide.