I'm not an Australian and gonna visit Sydney next week for more than two weeks for my work.
I've searched on the internet and found that the 4G Wi-Fi modem ($ 59 or $99) is fit for my schedule.
Is this 4G Wi-Fi modem available for non-Australian residents?
I'm wondering it is possible to buy it at the Optus of Sydney airport at the moment when I arrived.
There are not so many information on that because recent people prefer to use the prepaied Sim card rather than the modem.
I know Optus has stores in the major airports for arrivals, so you should not have an issue.
The Australian Government has requirements for ID to sign up for a prepaid service