So it is- I built one from scratch - much easier to work than stainless. But you should not underestimate the technical skill required to operate the vacuum equipment or run a mass spectrometer. Creating a spotlessly clean vacuum-tight system that can operate a vacuum levels close to that in interplanetary space is not easy or cheap.
There is posible to do atleast radiation and some XH with 1pa vacuuming. I have done it my desk and got some results. So quite big posibilites that garage people can do that experiment with single vacuum pump withouth mass spectrometer.
Biggest secret is where to buy nickel mesh and how sanding it and how apply Pd. Tap water is so full of stuff that extra purity is not needed.