Suggest checking WorkSafe https://www.worksafe.govt.nz/managing-health-and-safety/businesses/general-requirements-for-workplaces/first-aid/ for requirements as well.
First Aid at Work Feb 2020 resource has:
'You must provide a portable first aid kit in the vehicles of mobile workers if that is their workplace (for example, couriers, taxi drivers, sales representatives, bus drivers, inspectors). The kit must be located in a secure place within the vehicle, where it will not move and cause injury or damage in a collision."