Please list below where the nectars are found in USUM
Melemele Meadow, during the night (6:00 pm - 6:00 am in Sun | 6:00 am - 6:00 pm in Moon)
Royal Avanue, during the day (6:00 am - 6:00 pm in Sun | 6:00 pm - 6:00 am in Moon)
Hope this helped.
you can find various coloured nectars at the island medows in glittering patches. if you attempt to "use" these on oricorio, its form should change. the purple nectar happens to be in the flower patch at the centre of the battle royal area.