Helium-3 can be made on earth by fusing deuterium nuclei. Which is a lot easier than fusing Helium-3 nuclei, so if you can do the latter the former is probably a lot easier than going to the moon.
If it was easy to create Helium-3 via fusion we wouldn't need it in the first place. The whole idea is that He-3 fusion might be easier to harness because it produces fewer neutrons. And if we can't create it as byproduct in a net energy gain scenario this approach is only useful for spaceship fuel at best.
I guess, hypothetically, you could have giant D-D power plants producing He3 as a byproduct, which can then be used in smaller more portable applications like (space)ships.
