These are a couple of ways to use old technic visors. I looked for different combinations months ago, after seeing a few mike nieves uploaded on Flickr. These were two that I found after experimenting for a while, and as far as I can tell they're extremely versatile.
About this creation
The first combination uses tire inserts.
They can be seated in pin holes on pretty much anything.
The second combination uses revolvers.
Placing the revolvers parallel to each other, you should get a form like the one below.
The sight, and hammers of each revolver can be used to hold the visors.
I used these combinations on Nursie, and the scrap scooter.
Quoting Toa Likus
LEGO really needs to bring these pieces and the hydronaut visor back. So much more potential in them than meets the eye.
the only problem I have with them is the printing, a lot of the visors I have are throwbot visors, some have printed faces and some don't. if you want to use it for something other than a face, it'll look weird. I don't think the ones you mentioned have printing, though. but I don't have any of those.
Quoting Gale Winthrope
Lovely ideas here Cath. I am unfortunately lacking in the pieces to make use of them, but I applaud you on finding these :)