If you do need to have an Australian visa for a short visit to Australia, your travel agent should be able to help you get it quickly.
If you wish to apply for an Australian visa yourself without the assistance of a travel agent, you can do so in person at any Australian visa centre or by mail by sending in your passport and visa application form to an Australian visa centre.
Issued on the spot
If applying in person, visas can usually be issued on the spot, often within an hour and usually without need of a return visit.
Allow a few days for Australian visa applications by post and add the usual time it takes mail to reach the visa centre and return to you.
There may or may not be a charge for a tourist visa or ETA valid for one year, with multiple entries and up to three months' stay in Australia, but it's best to check with an Australian consulate near you.
With current security concerns, there may be changes in the requirements or process of getting an Australian visa.