Bling your kindle...... Grab a free Amazon voucher for 30% off Kindle Accessories
The Amazon promotional code works on the 75 or so products they have for kindles - stuff like covers, cases, speakers etc.
The voucher is valid up to a max discount of £30 so if you go over £100 its capped out. Doesnt work on Amazon market products but thats ok as for delivery to Australia you want it to be from Amazon SARL.
There is a 'restriction' on it in the terms and conditions, which is that you technically need to be UK based but I've just applied under my account with an AU billing address and with an AU credit card (you need to 'purchase' the voucher @ £0.00) and I get the voucher. You'll see a 'Your Vouchers' link on the top right hand side when logged into Amazon - its under that.