Hi Don,
Try an advert on the UK site www.speedsters.com
My brand new Standard GP exhaust was sold with my car in Feb this year.
I think the new owner sold it on via this site ( see sale section of this site)
http://www.spyderowners.com/forum/readmsg.asp?t=11424
The GP exhausts are now out of production and unobtainable
Spyders inc may be able you see www.718-rsk.co.uk
but they do a low level 'Zoomie' system that looks &*%432=
( Not Nice!!!)#
Failing that e mail Keith Stringer on the UK site he had a nice stainless system made.....but VERY EXPENSIVE.
see link to a picture of his former car
http://www.speedsters.com/images/staniforth-43b.jpg
Good luck
Magwa