You won't ruin it Snowy, it is just that Windex can tarnish the finish of chrome over time because of the ammonia. If you are wiping it right off the outside then you may never have a problem. I just learned about this negative reaction in Airbrush Action Magaine a few months back but there are many people who have never had any problems with it so I wouldn't be too overly concerned about it.
In regards to Simple Green, yes it is a household cleaner that we have here in the U.S. Their web site is here:
http://www.simplegreen.com/
I have not used the new lemon Simple Green on the opening web page of theirs, I have always used the green colored original formula, but I am sure the lemon would work great too.
I found this link on their web site about Australia so maybe you could call the number there or email them and find out where it can be purchased in your area:
http://www.simplegreen.com/global/australia.html
Mike
“Wisdom is the right use of knowledge. To know is not
to be wise. Many men know a great deal, and are all the greater fools
for it. There is no fool so great a fool as a knowing fool. But to know
how to use knowledge is to have wisdom. " Charles Spurgeon