I purchased this back rest for my bike as I have back issues and it works really well. It has been used only a handful of times and is in as new condition and is supplied with the fitting bolts.
The only reason for me selling it is because I am selling the Bike.
Fitting instructions are in this link.
https://youtu.be/SldiBnTLcOY?feature=shared
It only takes a short time to fit and is very straightforward with adjustability for comfort 
I can’t remember the exact figure as I seem to have lost the receipt but it cost me around £150.