All supermarkets around us (I'm in Auckland), seems to have stopped stocking the plain biscuits used in sweats making recipes.
Just like this one: https://www.paknsave.co.nz/shop/product/5208841_ea_000pns?na…
Not necessarily the same brand, but I've checked in Countdown, Pakn'Save and New World.
No alternatives or other brands are available unfortunately.
Same as anything else imported - either global logistics delay or, more likely the increase in freight rates would have shaved down what little margins there are on this type of products. Just buy Griffins, they are made here and plain sweet biscuits will practically always been in stock because the key ingredients other than the palm oil can be sourced locally.