Long live the Incandescent streetlights!Power Company: Eversource Startup Landscaping/LED retrofit business.
I have a few including the extended version to accommodate mercury lamps.
There is a top mount 50;s Westinghouse hood on ebay now. The admiral's hats as they call them come up sporadically and you might find one like I did. You would have a complete fixture then.
https://www.ebay.com/itm/Westinghouse-Street-Light-Hood/264645538898?hash=item3d9e1a7452:g:LuIAAOSwStheUz7Y