well.. how much do you want to pay? a new one is £265 for the standard height or £330 for the X-High.
So it would be a bit silly to pay more.
I paid £100 for a 2nd hand XX-High sport seat... they cost just a smidge under £400 new (plus post)
I thought that was an absolute bargain, particularly as the previous owner had a bit of taste and had recovered the thing and so got rid of the crap 'suede like' material (thats impossible to keep clean - his words) and added a layer of memory foam, as straight out of the box the seat was less comfy than sitting on a plank of wood. (his words again). But, most marvellous of all; recovering - got rid of the bloody TOURATWAT logo.
A GSA style seat with none of the faffing around replacing this that and the other.