Hi George
Steve here, I got your message and will answer soon.
It is unlikely that you will get a commercially available ships crest for the Wollongong in 1:72nd scale. At this scale the crest would be quite small, about 10.5mm high x 8.6mm wide and the rope circle in the center would be less than 5mm diameter. You are not going to see much detail at this size.
You are probably only going to get something the right size if you make it yourself. A photo or drawing program on your computer should allow you to shrink a larger crest (from the RAN web site) to the appropriate size. I would then just print a few copies onto plain paper, cut around them, coat them in clear varnish and stick them to your model. You may need to experiment with printer settings etc until you get something that is acceptable.
Steve.