It is surprising what you can get from the local Honda dealer. I have got some parts if not over the top, seals etc because of the US postage costs. UK postage is often much better value.
As for first class mail in the US, many ebay sellers don't even realise it exists. I have often pointed out to the seller if they will send the part this way, I will buy it and are only too happy to send it, but I think you are not covered by insurance, so not too costly parts worth the risk, but I am yet not to receive an item.
Many Americans do not seem to know how to use the USPS web site, go there and see why. It is the worst site to navigate. Number one problem, if your after a price, always takes you to the highest price first, you got to scroll to find the best price. Took me ages to work the site out, but they must of worked out I broke the code and made it even more difficult! USPS also do pre paid international boxes of different sizes, so if you are buying a lot of smaller parts from the one seller, this can be a more cost efficient way.
You can try Puds 4 parts in Victoria. I just got a carb kit from him for the honda 550, but many parts were not correct, could of got the same kit from the US with same parts for half the price, but was impatient, won't do that again.
There are many wreckers about, but you got to search and do a lot of ringing about. You could try Old Gold Motorcycles in Western Sydney and the is Jap Spares on the south coast of NSW.
You could also get a price from the guys who ship bikes in from the States for larger parts, I used Dead Dog Racing in Qlds to bring a bike in from the USA and he bought parts I needed across for me. There is also a guy around Tweed Heads who imports bikes for others as well as his own, he may also bring parts in for you, you can only try, got to think outside the square sometimes.
Hope this helps and not an overload of info.