Ideas for what we can do:
Theatres etc - go up to box office loudly asking 'where are the ladies'?' again and again as loudly as you can so the representative has to keep repeating the answer - if you're in a group, take it in turns for variety.
Ring an offending restaurant and book a table for six. Then ask 'I assume you have separate men's and women's loos?' then when they say no, say 'ah no, that doesn't work for us. I'll cancel that and we'll book at (name bitterest rival restaurant that does have separate loos) instead'. Get everyone you know to do it. Make sure you've blocked your number.
Come out of cubicle with full moon cup and wash it out in front of any men present (just pray they're not menophiliac).
Stickers. Lots of stickers.
Learn the statistics so you can recite the evidence of sexual assaults in mixed space etc etc whenever you're contradicted. 'In fact, Home Office statistics show that xx% ... ' etc.
Train your daughters to understand why we are saying no and to have the confidence to speak out. And your sons, too.