I was at my sons little league game and I sat down in one of those collapsible type camping chair. The ones for 20 bucks or less at K-mart etc... Coleman also makes them.
No pain. It was the first time since the pain began that I could sit down without pain. Seems to me, the chair supports you from the thighs and outside hips relieving pressure from the tailbone area. I use one at work. The problem is the chairs only last a few weeks or so before I have to repair or replace them.. They are not designed to be used the way I use them. I spend 40 hours or more a week sitting in them. I have 4 of them now. My job requires me to be seated all day long, I would have had to leave my job by now had I not discovered these chairs.
I suspect some of those lawn chairs that have bands running from arm to arm rather than back to front may have the same effect.
See Mac Sports
See also Comfortable chairs