Hi Chris,
...as someone who regularly gets things shipped to OZ your best bet is USPS, go to their postage calculator here:
http://ircalc.usps.gov
Select, "Australia" + "Package" and I typed in 3lbs to cover your shipping box and got these results:
Global Express Mail (EMS) 3 - 5 Days $28.00
EMS would be my first choice as it comes with a tracking number that works within Australia, I have heard its not so in Canada...weird...but in Australia when something is sent EMS I can check on the USPS tracking site and tell if my package is out for delivery or if its reached my local post office etc.... you can also use the Australia Post tracking website (
http://ice.auspost.com.au) to check it's where abouts but believe it or not the USPS site seems to be updated more often. My record was 60 hours for door to door service from the Mid West to Australia. Oh and delivery also requires a signature.
Global Priority Mail Flat-rate Envelope (Large)4 - 6 Days $9.00
This would be my second option, I usually use it for books, but you can use it for items that aren't too expensive as well. The flat rate is for anything upto 4lbs so its a budget good option, if you have a smaller item you can send it via the "Small" Envelope which only costs $5, the cheapest and fastest way to send something to OZ.
Customs Declaration: Make sure you write it is a "second hand camera lens/parts" and declaring the value is upto you. Keep in mind Australia has some interesting Custom rules....like you can send $1000AUD worth of items via regular Air Mail without any taxes being levied, BUT the maximum value of items you can send via a "Courier Service", and this includes EMS, is $250AUD. Ofcourse the Catch-22 is that if you had something worth $1000 you would want to send it via EMS as it has both tracking and insurance AND is so fast it rarely has time to go "missing". Also any levied value on EMS in Australia includes the cost of shipping, yep we get taxed on the shipping which really annoys me as its a service originating outside of Australia which has been taxed already and paid for by the sender.
OK hope this helps.