Have a look through Holden Vintage's on line catalogue. There won't be a specific RM lamp, but there are similar Lucas repro items listed. It will be necesary to isolate the lamp electrically and run a negative return wire; not too much of a problem if the wing panel is fibre glass.

I'm glad you remembered the negative wire roy. About 10 years ago when I rebuilt RFW14, I put the fog lamp back on it. The foglamp would magically go on with the engine revving and the pilot light went out, despite it being turned off.

I had to check for the bastard feed, it was the foglamp. It had been fitted with a single pole bulb previously and that was shorting through the lamp body giving a feed to the chassis. there was another wire touching somewhere which caused the lamp to light randomly. I changed the bulb for the correct type and the provlem went away. I never did find the other feed, may have been in the trafficators.

My bus number (if any): RML2532

I should add that I haven't checked the wattage of the bulb required for the repro lamps in the catalogue, however I suspect that the RM one is of fairly low wattage. I don't know the amperage rating of the Arrow switch nor of the wiring to the foglight, but I suspect that the switch is capable since it is the same as used for the headlights and my guess is that the wire is the same size. The reel of 28.030 I have recently purchased is rated at 25 amps.