mlts22 wrote:
If you are going to be there for a bit, why not rent a "turdis", or a plastic bathroom that is plopped down by a sewage company, then picked up after the event? You can padlock the door so it isn't a public restroom. Cost is probably $75-$100. In fact, I've rented one for about four months for about $400, with weekly pump-out services.
Of course, if you want something you can use at multiple events, I'd probably look at the Cabela's solution as mentioned above.
The problem with that is that, when people see it, they assume it's a public washroom and you get to turn people away every few seconds, especially during a parade like a St. Paddy's Day Parade. At events like that, you want something more inconspicuous.