[Australia][Source] 20 or 22K Gold solder

Hi, I am not sure where to direct this question but I am presently
in Australia and have been told that I am unable to obtain 20 or 22K
solder here, in fact I was told it is not available. Having worked
in the US I know that it is, however this does not help me whilst I
am here and I was wondering if anyone could tell me how to make/the
formula for 20 and 22k solder in easy, medium and hard. I would be
very grateful for any or books where I can get this
Very kindly,

S. K. Lehmann