McMaster does still ship to Canada, purchased some items this week, however, we are an established customer and have been for about 4 years. It must be a real pain to live in Australia when what is easily available in Europe and North America becomes almost a specialty item. We have this issue to a degree in Canada but obliviously nothing like you do in Aussie.
I get good results welding stainless when using stainless 310-16 or 316L rods. The slag floats to the top and is easily chipped away in big sections without inclusions. SS is a good conductor of electricity and heat which is why I like to weld with SS rods.
They also work well on cast iron when I have had to make repairs.
stainless is an extremely poor conductor of heat and electricity which is one of the reasons why it is such a pleasure to weld
to prove my point try fusion welding of copper, gas or tig to see what I mean