heavy duty whip air hose

Yes, it's called hydraulic hose. The "one wire" variety is fine, more flexible and more than adequate pressure rating.

tried that, too stiff. Tires lower arm out. We do this ALL DAY for weeks on end.
Karl

Ok, then look at some of the hoses made for SCUBA regulators, they're tuff and flexible. 140 PSI is the normal feed to the second stage regulator.

See if your local SnapOn guy has some and see what his guarantee would be. Ditto MAC, Matco, and Cornwall tool trucks.

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.
Repurposing is the R.C.M way.
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