There are no wholesalers for most guitar products. You get them directly from the manufacturer.
For exporting US guitars, your best bet is to contact the manufacturers directly anyway, as many have official and exclusive representatives in various export markets.
You might consider looking at a site like MusiciansFriend.com to get a feel for what the most popular selling brands/products in the US are, then cross check that with what you're able to find in Oz. If you find a company that appears to have little or no 'footprint' down there, you might be able to work out some sort of distributor-level agreement with them where prospective retailers are directed to you.