Spencer, Check with Utopia, I purchased 2013 ST backrest from them about 4 years ago. Hopefully they still sell this item.

Installation is kind of involved, seat comes off, cover comes off seat, large bracket installed, cut hole in roam and cover, reassemble. The instruction sheet is pretty góod, but it definitely takes some courage to cut the cover. You will need a powerful stapler to refasten the cover.

If you are queasy about this, I think an upholstery shop would install the backrest.

The backrest is fantastic, looks góod, works as advertised and has provided hours of comfort. I recommend the removable version, it folds down as well as removable.

You can do it!!!