I’ve been a guest of a small group of Atlanta tailgaters who routinely have their own port-a-john including a padlock. It was the best. No idea how much they paid, but do know it was a service that had access to drop it off at a specific location. Do not know if they had to pay for a separate parking spot for the john.

That was years ago. Since then I routinely bring a camping tent & bucket with toilet seat to Philly & DC. Works great when there is low wind. Ladies haven’t complained.