Well...it looks like one fitting has already been replaced with a brass barbed fitting and a hose clamp.
The easy DIY way would be to buy some air hose (or perhaps buy a 25' or 50' air hose and chop it up), some barb x male NPT brass fittings (available lots of places, McMaster, local hardware, limited selection at Lowes/Home Depot) and some hose clamps and go at it. For a fancier DIY install you could buy Otiker clamps and pliers instead of hose clamps.
....or take off the hoses you have and find a hose shop, they can make up replacements.....it appears that all of the fittings are pipe thread (NPT)
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