Anyone with information about the location of the vehicle is urged to contact the Operation Tailor team at Hamilton Police on 07 858 6200 or call Crimestoppers on 0800 555 111.
He died while shielding her from bullets. A 17-year-old, Izaaic Hauwaho, was shot four times while also trying to protect Marfell.
A source later told the Herald the gunmen asked for Marfell's father and senior Mongrel Mob member, Mark Griffiths, at the door before firing an unknown amount of shots wounding everyone but Griffiths.
Hauwaho is in a critical but stable condition in Auckland Hospital, while Marfell, who was shot in the leg, is now recovering at home.
Nelson, who was not a gang member, appeared to have died simply trying to save his girlfriend's life.
And on Friday, July 13 the beaten body of Mitchell Paterson was found submerged in water below the McLaren Falls Bridge.
Police are also seeking sightings of a vehicle seen in the area at the time.
Pitkethley this week said police were also keen to hear from anyone who had seen the light coloured Nissan Terrano being driven between Hamilton and Tauranga between Wednesday July 11 and Friday July 13.
The 27-year-old Western Bay of Plenty man is in custody after being charged with being an accessory after the fact of murder by helping another suspect dispose of his body.