Greg,
Still looking for a suitable light. The Narva one is not ADR 1/00 which is an approved ADR reversing light. The 90810 is a marker light which is ADR 49/00. I spoke to the engineer about these lights and as I thought they would not be suitable for a reversing light.
If want to know (or be confused) about ADR's go to this site
http://rvcs-prodweb.dot.gov.au/ and click on Australian Design Rules.
Warren