I ended up having it made. Ryan runs a workshop from home (just out of Waiuku on the Awhitu Penninsula) part time specialising in stainless exhaust fabrication and has a strong sideline in resoring and building 4WD projects from what I could see.
Super-friendly, quick, and reasonable but not cheap - $220 all up.
Exhaust is in 316 and is an exact copy of the fabricated item it replaces. Ryan machined the grip rings on the barb for the water inlet - nice attention to detail.
He is contactable if you have something in mind - 027 289 4007