After switching the sights on my Glock 17 and finding no problem chucking the slide in a wood lined vise and tapping the rear sight into position with a mallet and wooden dowel, I thought a rear sight tool would be far more convenient if I want to make an adjustment at the range. But... For something I'd use so rarely, they seem pretty expensive.
So I designed one and printed it on my 3D printer. Being mainly plastic, I doubt it would hold up to as much use as an armorer would need, but since I only anticipate ever using it a handful of times and it's been effective to easily nudge the position of the rear sight, it's working for me.
If there are other users with 3D printers that would like the files to print their own, I've uploaded it to Thingiverse: http://www.thingiverse.com/thing:33587