The moon, solar winds, nuclear fusion, nuclear fission, the lithosphere, other planets, local sources.
Currently the easiest way to get it is as a byproduct of natural gas drilling. But the planet has been outgassing it for, geologically, a very long time. The low hanging fruit might be running low but if there is a demand it for then there will be someone willing to sell it to you.
Currently the easiest way to get it is as a byproduct of natural gas drilling. But the planet has been outgassing it for, geologically, a very long time. The low hanging fruit might be running low but if there is a demand it for then there will be someone willing to sell it to you.