If you're not paranoid about using brass, and are willing to be careful around hot fittings, try coupling item #6739K68 from McMaster-Carr and the mating plug #6739K57. I use them with high-temp tubing and they work great. I have the plugs on my vessels, pump and WIC inlet, and the right-angle couplings on the hoses. They're very durable and considerably more affordable than polysulfone or stainless.