Australia Post will put a card in the PO box, and you go to the counter and collect and sign for the parcel.

But,  there is always a but,  and it applies to PO boxes and your home letter box, it depends on if the postie actually complies with the signature request.   My favourite was the time I had a $800 coin (signature required) article dumped on the doorstep,  and a $10 rubbish item taken back to the PO the next day for collection.   So yes they can, the question is will they.

But I would definitely use the PO box if thats what they have offered,  very little chance of that getting picked up by a random