Try a PM (private message) to Mitz at the Cougar Store. He should be able to help one way or another with advice.
Link: http://www.350z-uk.com/forum/94-cougar-store/
http://cougarstore.co.uk/index.php?main_page=product_info&cPath=1_10&products_id=112&zenid=bcaa60565806895c2c0f2d2ff1b32aee
Your other option is to take the car to a custom exhaust manufacturer. Somewhere like "Longlife" will be able to make you a custom Y-pipe to fit which I'd imagine would be well within your budget.
I had a complete Cat to back exhaust system made at Longlife for a Civic Type R some years ago and it was £300 for everything including fitting.
One in West Thurrock, Essex ~ Link: http://www.longlife.co.uk/depots/stainless-steel-exhauts-west-thurrock/