Fire extinguisher clasps seem to be easily broken, and I had a couple which I tried to secure using bungee cord, but they were not what you might call quick release. The Quick-Fist clamps did the job admirably. They are made of thick rubber in two sizes. The largest will hold cylindrical, or oblong objects, from about 2½” inches to 7½” inches in diameter and the manufacturers claim they will even hold dive bottles. The smaller model is advertised for objects from 7/8” inch to 2¼” inches in diameter, like boat hooks or dinghy oars, but I actually found they would only fit 1”inch to 2”inch diameter items.
I cut the original strap off the extinguisher holder and screwed the larger size Quick-fist below the holder, then pulled the securing band to the tightest of the alligator like serrations. This held the extinguisher in a vice like grip and I then cut the excess off both the serrations and the release strap. A quick tug on the strap unhitched the clasp and released the extinguisher.
Retail prices for both sizes are $14.99, but the smaller size has two holders per pack
Davis Instruments, Hayward, California 1 800 678 3669 with distributors worldwide