Found 2 in the for sale section but seems a bit too far for you? --> http://www.350z-uk.com/forum/213-350z-parts-for-sale/
Just back box ->http://www.350z-uk.com/topic/108430-for-sale-standard-exhaust-backbox/
Mid-section + backbox --> http://www.350z-uk.com/topic/108004-standard-centre-pipe-and-back-box/ (but they are welded together, will be difficult to ship)
The K1 is sold now -> http://www.350z-uk.com/topic/108583-japspeed-k1-with-bungs/
Get a 2nd hand OEM standard exhaust first maybe? Ask Zmanalex or Jon@Emperortuning if they have one?
Most likely you will need Y-pipe, mid-section and back box.
Looks like the product has been discontinued hence seller bumping price up to make a profit!! I got mine for less than a tenner shipped.
Try this maybe (build up a few coats)--> https://www.amazon.co.uk/Surface-Sealant-Coating-Repellent-Plastic/dp/B00A3S1RGU/ref=pd_bxgy_263_img_2?ie=UTF8&refRID=B7SEPM0366PGVWDYN1NZ. Make sure to keep it away from paint (just in case)
I just polished mine last week using Maguires headlights kit (https://www.amazon.co.uk/MEGUIARS-G1900K-Headlight-Restoration-Kit/dp/B001O7I7FS) cost about £25 ish. Follow the steps to sand your headlights slowly until it is white ish. Yes, this might sound scary but it works. Completely transformed it and it looks almost new. Make sure you use some detailing masking tape around your headlights to avoid sanding your paintwork. Just make sure you seal it with some UV wax (Turtle Wax ICE - http://www.carmaniaonline.co.uk/turtle wax ice synthetic paste polish kit- turtle wax- ice-car polish) I build up around 5 layers of wax so that the newly polished headlights are protected against UV which is the root cause of it turning yellowish
Edit: DA = Dual Action (bed time story here explaining http://www.detailingworld.co.uk/forum/showthread.php?t=63859 )