no one has any right now, only one seller i know was able to get them. So I would say VERY rare. I need to look into how they need to be kept. I thought they are cold water fish...not sure... Fishbase shows they are criticaly endangered, but not in CITES list? Sometimes Fishbase also lists the "tropical temp" but it is not accurate. I read that the Aussie lungfish could live as low as 50 degrees, but Fishbase shows it can live 78 degrees or higher...so it was not accurate. Here is the info on the murray cod in Fishbase. Note 180 cm, not sure how fast it grows.
I think Fishbase got it wrong. While limited somewhat in their range, and nowhere near as common as they once were, they are not critically endangered. Competant anglers can still go out and reliably catch them, and they are bred commercially for restocking and as food. It is the Trout Cod (a very similar species) that is endangered.
And they are not really a tropical species. While the one I kept did fine in a tropical setup, their natural habitat has tempts that go down close to 0 deg Celsius, and as high as 40. They are commonly caught when there is frost on the ground.