Technofreak:
I only get to Aussie once or twice a year for work and perhaps one other time for personal reasons. Covid has prevented any work trips till now but am about to head over for work shortly so checking out my options. The likes of Optus is my first choice but we'll be like we're in MIQ while we're there so there'll be no chance to buy a new sim card unless they can deliver it to the hotel.
NZ travellers can come into Australia without quarantine (assuming they follow entry rules).
It's better to just buy whatever $30 SIM has been discounted to $10 or less at Woolies or Coles.
Otherwise, look into ALDI Mobile (sold at ALDI stores, activate online) which lets you keep the SIM alive with a recharge of $15 per year (you can use the credit you buy to put into a plan & buying more credit refreshes expiry again).
https://www.aldimobile.com.au/collections/plans