40% for women 18-24 are obese or overweight so unless you're in the cbd of any major city there are plenty of fatties especially in regional Australia. Australia is a developed country so we have a higher obesity rate but overall they aren't as big as American girls and we generally don't have Walmart fats just walking around. You can always date up in age because the obesity rate increases as age increases.
If you try dating apps, as I've said many times of this website, use Hinge amd only send likes to fatties. After a few days of using it the algorithm with see that you kike fatties and only show fatties.
Don't feel disheartened if you can't find and fat gf right away you just need to be patient and don't lead with sexual stuff if you actually want a gf.