Note that there were many shapes to spark arrestors. Here's a link to a Heisler on Vancouver Island, British Columbia showing a different setup, including what appears to be either a steam extinguisher conduit or something else.
Thanks, guys. You've given me a good starting point to look. Actually I'm looking for something more like this. I found a spark arrestor assembly in an old parts catalog for a 2012 version of an HO scale Mantua 2-6-6-2T logger that would fit the bill. It's listed as being made up of four part numbers: mo368, mo403, mo370, mo369. This is exactly what I'm looking for, but preferably as a brass casting. I'm thinking about adding a little visual effect to an old logger by installing a small smoke generator and an randomly flashing red LED to simulate cinders igniting to flame in the spark arrestor. The problem is a lot of detail parts makers are not in business anymore, even though their parts catalog is still floating around on the web. Oh, well, it was just a thought.