UPDATE: My new version of an single printed joint hose component is here:
I couldn't find an acceptable easy-to-print and strong flex hose, so I made this one. It's a solid part that has appropriate reinforcements around the base where it's weak,.. seriously, it takes a lot of force just to snap these together, but they're fairly air tight and they hold their shape pretty well. My big desire in making this was a piece that wasn't just a shell, but was actually solid inside, so I made this from scratch using FreeCAD to end up with good wall thickness and also very tight tolerances.
I print them with a raft, open side down, and it's best to snap them together if you warm up one side a bit. You'll get the hand after a couple pieces if your hands don't hurt too much :) Don't force them straight on, kind of wobble them on in large motions.
Another thing I do is set the diameter of my filament to .32mm so that it overprints the walls and creates an even stronger part (it's actually .4mm)
Once they're together, if you find that some air is slipping (because they were too cold when snapped or because the material you used fractured) you can either put a bit of heat shrink tubing just barely over where they connect, like, maybe 3/8 or 1/4 in wide band over where the ball and socket meet, but just be sure the majority is on the socket side and not the ball side, and when you heat the heat shrink, don't move the pieces or the PLA joint will get weak and tear.
I'll post a picture of that if anyone is interested. Another thing you can do is dab a little acetone on the ball after they're connected (you have to let it work in between the ball and socket,) let it sit for 5-10 seconds, then move it just a bit around and blow on it to evaporate the excess, that gives it a nice smooth flow, but it does reduce the friction slightly depending on how much you add so be careful. It improves air leakage too though.
I'm feeding these with an air compressor, so, they're quite strong and air-worthy, I hope you enjoy! :D