Easyshare might be worth looking into. I have used it for non-ABN purchases, their rate is 2.5% for Amex.
You need to be a little but hacky though.
Their service is geared for sharehouse tenants and is designed to add credit cards from members of a household, and zaps their monthly rent to the real estate agents bank account automatically to save tenants fiddling around with EFT transfers every month.
Their system accepts any BSB/Account as a rent payment destination, and you can put one off payments through using the same setup too. Ping support if you find it a bit fiddly, they have always been really helpful when I've needed them.