There was a official kit for installing the light/beacon. Although I have yet to see an original picture of one in use, on a vehicle in service. Most every picture below is a field expedient of some kind. Rear mounted... Windshield mounted, cowl ... etc...
The pictures below are a grouping of all the pictures I have with some kind of extra beacon light. This doesn't include MP lights which will be a whole other MP related section.
"Correct" installation kit below