Chris,
Having spent dozens of hours sourcing my early lights, IMHO i feel i can provide the correct answer.
In fact, there were an even earlier style of light fitted, than the one you posted a photograph of. If you check out photos of the prototype cars you will see what i mean.
In your photograph the lights are Lucas units, model numbers
Amber Unit & Red Unit: L691
These are the same units as fitted for turn and stop, to Austin Healey 3000.
You can find these units, remanufactured on eBay quite often.
They are also available at
www.holden.co.uk
where you will find an impressive supply of remanufactured Lucas parts.
Do a search on Holden's site using L691.
Hope that helps.