If it's LHD, then buy an off the shelf header and even full system for it. That's easiest, cheapest and the best factory fitting system, but you just have to source and import the parts.
A fully fabricated system could cost anywhere from $2K-10K depending on what you want and expect all sorts of bracketry welded on here and there and pipes going places that may interfere with the other components if the car is not complete when the system is fitted.
Some good guys out there and some fxcking crooked morons too.
(click on the amp!) Post pictures! ..or it never happened.