Mirroring shapekeys.

I’m trying to mirror shapekeys.
If I have say, the right eye closed, set the slider to one and add a new shapekey from there, then the exact same shapeky gets copied as a base for my new one, which is what I want.
Now, I want to mirror the vertex locations of the right eye, to the vertex on the left eye. the mesh was completely symmetrical, so I figured this should be possible using the mirror vertex/weight script.

I haven’t gotten it to work, farthest I got was ending up with a selection of vertex that are the same for the right and left eye, so I can see which vertex are in fact in a different location.

I know I should be able to do this by making one shapekey with xmirror on when modeling to get both eyes closed, copy that one, and make some new vertgroups, but it seems unintuitive.
Isn’t it possible to just copy the location of the vertex that form the closed state of the right eye over to the left eye?

Deleting stuff and mirror from there isn’t really an option this thing is fully rigged, don’t want to redo it.