When I first got my Fairmont limb lopper air pruners twenty years ago, they came with a heavy duty swivel air whip hose with a wire spring reinforcement at the metal to rubber hose junction. They lasted five or more years.
Ever sense, we've been replacing this item constantly. Anybody seen a super heavy duty air hose whip?
Rather than depend on the spring alone, I would get a double-swivel for the end of the tool so it can't kink on you, then use the lightweight Polyurethane "Roofer Hose".
You can get it in 1/4" and 3/8" ID,depending on your flow needs, and various lengths. Put QD's on the ends and you can swap the hoses out for a spare if they get wiped out in the field - fix them in the evening.
If you really want the spring on the ends and a nice coiled line, go to a good Auto parts Store that has Truck Stuff, and look in the Air Brakes section. They make a wide assortment for between a tractor and trailer, and they come with the strain relief springs.
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