Thanks, Raven, that's a good-looking substitute.

Sorry, I forgot to mention the Atmosphere Strength setting on the lights (see screenshot). This value multiplies the Volume_Density value on the Atmosphere node to give the strength of the atmosphere effect for each light. The default value for a new light is 0.02. In my render it was set to 1.0. I noticed that I had another very low intensity spotlight in the scene.. the Atmosphere Strength for that light was still at default, and it had no visible effect.

You can reduce volumetric rendering times (with some loss of quality) by increasing the distance between volume samples using the Volume_StepSize parameter. Mine was set to 1.2 inches... note that this parameter uses whatever units you have selected in your Preferences, so you have to convert that value if you are not using inches.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)