Hello Gav.
I can make one adapter for you. All I need to know is the type of your PSU (AT or ATX). The shipping costs from Brazil to Argentina is US$15.6, plus 4 for Paypal fee. The good is for free, of course.
ATX2 don't work, it need a special circuit in order to work (like a "thick" signal, but in that case who wants the signal is the PSU).
But the schematics is pretty damm simple.
Have a look:

Just in case, here is the link to the whole page:
Ian Stedman's Amiga hacks