So I saw this online and thought of SD and other builds and figured I would pass it along. This is a mount a guy sells but it would be easy enough to fabricate one. I like the quickness at which it could be deployed.
So here are the pieces:
The top "bracket" in this pic has two slots between the welds for a hose clamp which goes around the extinguisher. The slot on the left hand side of it rides on the pin in the bottom bracket. Then the push pin goes through the smaller holes and holds the extinguisher in place.
Here is a pic that shows it holding the extinguisher:
And here's what the "finished product" looks like:
Anyway....figured it was a pretty good idea that some could use.