One shortcut I've done is to buy hose barb fittings at the hardware/plumbing store, and turn back/thread the base to suit what it needs to screw into. Other times, as Jo said, just turn my own from some round bar. The barbs are not critical dimensions, just needs to have a small enough end to start into the hose, and taper out into some steps. I usually wrap a little wire around the tube to keep it from blowing off under pressure.