Gramps-simple you can't. By the way I am in the Caribbean as well. I have now a Caribbean ATPL with IR from my US Licence, my Aussie will expire shortly but will not affect me. I will return to Oz in March to do my renewall. Its the only way to do it, I dont think there are any ATOs outside Australia.
Send a Pprune message to me for more info.
Regards
Sheep