I´ve seen scissors sharpeners around, I guess the ones with ceramic rods should work, also the Sharpmaker has a scissors setting, as far as I know they all have fixed settings which may not be at the same angle as the scissors have to begin with..
I know some people sharpen with power tools, some do a very good job, some don´t
I cut my own hair and sharpen my own scissors, here´s how I sharpen:
I open up the scissors and lay the blade on a table with the edge up, holding the handle (finger hole of that blade) in my left hand, out of the table.
Rotate left or right so that the edge bevel is horizontal.
Holding the edge horizontal, I take a hone in my right hand and run it along the edge keeping the hone horizontal also so that the edge is worked evenly, this has to be done with precision.
Once I feel it´s right (slight burr along the flat side of the blade, inside of the cutting edge), I lay the blade flat side over cardboard or paper and strop a few times.
Repeat on the other blade.
Some tips:
Medium or medium coarse hone leaves the edge a bit toothy which makes a good cutter, medium is probably better for cutting hair.
As with knives maintaining the angle is critical.
The back of the blade may damage the surface of the table, it might dig in a bit from pressure of the hone as you run it along the edge, so don´t do it on your good table and you may want to put some spare wood or something under it.
As with most things, better practice with a cheap one before trying on the good ones.
If you can hold the angle correctly, I believe you can lay a hone on a table and draw the scissors along as with free sharpening knives. To me its easier the way I do it because I can see when the edge is horizontal and its easy to see that the hone is horizontal too.