[TR] TR3 Backup Light

[Carl TR]

Finally getting around to this...
 
I have an original [in box] TR3 Backup Light (Lucas L494) that I will be mounting on the project.  I know that there has been discussion on the list of different ways to mount/wire it - but I can't seem to find it in the archives.  
 
Option 1: Add an inhibitor switch on the tranny that is engaged when in reverse.  Not really an option as I don't want to drill/tap the tranny top cover.
Option 2: On/Off switch similar to the push/pull on the TR3 center panel - upgradable to the one with the light
Option 3: On/Off toggle switch
Option 4: Button type on/off switch (engaged when depressed - similar to a door/interior light switch) mounted somewhere on the tranny cover to be engaged when transmission is in reverse.
 
I would like to go for #4 - but not sure if I can engineer it from scratch.   #2 or #3 would be the easiest.
 
wiring is fairly straightforward.   Green from an appropriate power point (ignition or elsewhere) to Switch and from switch to lamp.  Ground from lamp to body through fixture (andin my case also a secondary ground to an earth clip on chassis.  Although the power feed is ultimately fused, I will probably include an in-line fuse between switch & power for safety sake.
 
Any thoughts out there? 
 
Thanks
Carl