Have you sat on a Corbin? they are rock hard. Maybe they work if you have a big butt but for a skinny runt like me they are not comfortable? Luckily I find the stock rider seat fine.
I took the pillion seat off and added an inch of foam to the height and 2 inches to the width and got an upholstery firm to make a new cover. I couldn't find a larger sissy bar so ended up making my own and fitted an aftermarket pad. I kept have kept the ability to change the sissy bar back to stock. The wife hated the old seat, loves the new one.
EDIT: Just saw that you have seen my previous post on this, so I guess you are still looking for an aftermarket solution. Good luck