FPV Goggle magnifying glasses holder (Cyclop Eye 5)

This is a holder specifically for these lenses: http://www.banggood.com/4-Lens-Headband-LED-Head-Light-Magnifier-Magnifying-Glass-Loupe-p-950353.html

They will clip on. If it's too tight, you may have to file the opening a little wider. Use either a M3 or M4 screw and a nut/lock nut.
For me, the 2.5x ones work best with a 5" monitor at about half way down the slot.
It should be easy to use this lens holder with any DIY facebox by simply providing a 4-5mm wide slot at the top.

The biggest advantage is the highly clear image, without the loss of quality from a fresnel type lens. There's still some pillow effect distortion at the the edges, though, depending on which lens is used.