Where Can I Buy Bulk Australian Coins In The US?

I would put an ad in craigslist for the city you are going to and see who responds with what. I don't think there is any dealer in North America holding a bulk lot of Aussie coinage. You may find some people have a few.

As a very general rule, you can only buy "bulk coins" from the country that you are in, as there is usually very little need for bulk quantities of coins to be travelling overseas - unless they're being melted down for scrap, in which case you still won't get to see them. Money-changers worldwide tend not to deal in coins - even for currencies such as the pound and euro where the highest denomination coins still have considerable buying power.

Some of the larger coin dealers that handle foreign coins might acquire enough of any one particular country to be considered "bulk", and they might even have them sorted by country and (if modern) sell them to you for near the exchange rate. You'd want to try the dealers in places where Australians are likely to pass through: NYC, Greater Los Angeles and Washington DC. There ain't gunna be many Australian coins findable in North Dakota.

There was a poster on this site a few years ago who had several thousand for sale in the U.S. - it seems he obtained them over here, so like that!