Welcome to our forum, there is lots of good info here.
Do the demo seat thing first at your local dealer first.
Then try the aftermarket seat guy's, then the shock guy's.
H-D with some with means Hundreds of Dollars, get ready to part with some $$$.
I’m also one who suffered from tailbone pain and would have the rush of pain, when lifting my rear up off the seat when stopped? All has been solved since installing my new Russell DayLong saddle. I have put over 750 miles on the new DayLong and I’m very very pleased. Daylong is one of the answers. Wish I had tried the DayLong years ago.