You can ask your GP. It seems a reasonable request and they are struggling to get the last remaining over 75s to have it so there must be spare supply.
You would get one in September anyway so I see no reason in these circumstances to say no if like me it is now 8 months since your last one - being over 70 but not qualifying for the fourth jab by age.
Cases here are going up fast now. Just as we stop recording most numbers.
But England hospital patients over the weekend are up from 9329 Friday to 10,658 today - which is up 2836 in the past 7 days - over a third in the week.
That is the highest level in 10 weeks so gives reasonable cause for you to ask at least imo, Regardless of the levels likely in New Zealand. Just for your own health reasons.