G’day Mate, and welcome to the forum.
In Australia the Model 52 mags are near impossible to get.
At gun shows they come up occasionally (used) for $100~$140, and you need to be quick. Compare that with the US at around $60.
You will not see any on e-bay in Australia as it’s against their policies here.
Your best bet is to put a wanted ad on usedguns. I’ve done alright with my wanted ads in the past, the costs of $20 and it’s been worth it.
A few years ago when I started shooting WA1500 pistol with the 52 I had 4 mags, I had to load from the pocket in some of the stages. I was desperate for more and started looking for a gun with 4 mags, just for the mags.
I now have a few 52s and a dozen or more mags, however only 8 modified for 6 rounds which I use for WA1500.
With any luck one of these very friendly US forum members will offers to sell you some. Getting them in the post in Australia is ok, if customs stop them you will need a B709 and it’s much safer to have it ready. Brownells did have them for about $60 and may post if you provide the B709. Send them an email they can only say no.
If you cannot find some in a few weeks send me a message and Ill check exactly how many I have. I don’t really want to part with any however on the other hand I also know how hard they are to come by.
Cheers.