Fire extinguisher clasps seem to be easily broken and I had a couple that I tried to secure using bungee cord, but they were not what you would call quick release that might one day be important. 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