Right now we get helium by distilling it out of natural gas, which means that we only tap a tiny fraction of what's actually present on and in the planet. And although right now we're using helium faster than we can extract it from the dwindling supply of natural gas, that doesn't preclude the development of other methods and sources in the future (and, once the supply is low enough and the demand is high enough, somebody will put up the money to figure it out).
I work for a company that makes it more efficient and safer to throw away natural gas. It's nowhere near as rare as you think, in fact, in drilling, it's considered a nuisance more than a product of the well. It's like saying we have a dwindling supply of mud.
At one point, oil companies actually gave it away for free.
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.
Right now we get helium by distilling it out of natural gas, which means that we only tap a tiny fraction of what's actually present on and in the planet. And although right now we're using helium faster than we can extract it from the dwindling supply of natural gas, that doesn't preclude the development of other methods and sources in the future (and, once the supply is low enough and the demand is high enough, somebody will put up the money to figure it out).