Presumably you are in Australia, coz of where the post is.
Have you tried Vanbar?
Quite some time ago I was fiddling with a friend doing colour neg chemistry about the time RA4 was being introduced. I seem to remember using Ferric Sodium EDTA which was a yucky sick looking powder. It did the job.
Vanbar on their Bulk chemistry site list various EDTA salts and acids.
Better yet, telephone their North Melbourne branch on a Wednesday (I think) when their chemist is there and speak directly to a heavy European accented, photo chemist.
Worth a try anyway.
I've been starting to re-stock my B&W chemistry of late and Vanbar have been quite helpful. If you live in Melbourne or Sydney, you can pick up and eliminate courier or postal charges.