Here are photos of some headlights of the type I think you need. I have had a good look at them and I cannot find any manufacturer or Military markings, so I think they are civilian tractor units. Before you ask, No they are not for sale.
Did British Jeeps have one or two headlights, Yes. It seems to be unofficial and whatever was to hand - it was wartme. Check out wartime photos for details as to what is common. I do not know of any manuals on the installtion and assume this mod was done at unit level with any parts available, hence the use of tractor headlights which could have come from the station's David Brown tractor, for example. Try a classic tractor parts source as these headlights were common in the 1930-50 period.
About the best I can do.