I typically order my foreign cash for travel using this platform already (as have found they usually have the best rates around for foreign cash).
This deal/code was marked expired, but I tried it anyway and it worked: https://www.ozbargain.com.au/node/215910
So if you are ordering A$500+ worth of foreign currency I would be surprised if you find a better rate than on offer here using the code.
I know you can get better rates using some credit cards, but I'm old fashioned in that I like to use cash a lot both in Australia and when traveling. Also ordering cash allows you to lock in the rate, which is not always a bad thing given the recent volatility in the Australian Dollar.
Happy travels :)