I just finished installing these today, I had made them quite some time ago using the glass from my truck's original mirrors. I found that if you drill through the black plastic backing the mirror glass and remove the adhesive foam goes, you can put LEDs behind the mirror glass and have them shine right through.
I used LEDs I had sitting around from the old 3rd brake light for my canopy. (They aren't great, so thats probably why a tiny little brake light needed 30+ LEDs). This means you can't really see them in the daylight, but they are cool in the dark. I can put up with this considering it didnt cost me anything to do it.
Here's a video:
And a picture of the glass when not lit: (Note that these are completely stealth with no cirles in the reflective surface like the factory mirrors)