Thing 53870 works great to get at the top of the screw adjusting the Z zero point, but that wasn't our problem. We have the locking nut also on top of the Z plate, and it's quite difficult to get at that to unlock the screw. This funny-looking bent open-socket wrench slides over the nut without bumping into anything, as shown in the photo. Once unlocked, you can spin the screw to the desired height with your fingers -- then use the wrench to lock it again. Really quick Z adjustment!
An easy print in PLA, but use 25%-40% fill to ensure the open socket is stiff enough to work smoothly.
I actually designed, printed, and have been using this since the middle of 2013, but didn't post the design because I wanted to re-do it to look less odd. Never got around to doing that. Anyway, it's useful enough that it doesn't matter how odd it looks. ;-)