The space elevator to the lunar surface that 'could be built today'

Both literally and figuratively, a pie-in-the-sky proposal. For the moon, a "geostationary" orbit isn't possible because the moon's rotation is tidally locked to the earth, so the moon's orbital period is 27.3 days. This means a lunar "space ribbon" from an orbiting craft would perpetually drag across the moon's surface -- it could not be attached as in the usual space elevator scenario.

A craft parked at the Lagrange point would be too far from the moon to be practical, and there remains the issue of differential rotation between the parked craft and the moon.

For the earth side, they're planning a balloon at a 2 kilometer height. That is at least feasible. But neither of these proposals represents a way to get cheaply to the moon, their promotional literature notwithstanding, because of the huge gap between the earth's tethered balloon and the other terminal orbiting the moon.

And all of these ideas require materials (for the tethers) that do not exist now or in the foreseeable future.