I bought mine from Amazon. Mmtheyagree are a circular disc, with many flat LEDs on them. The back has Velcro and it comes with a round disc with velcro on one side with adhesive on the other side.
It is meant to mount on the opposite side from the battery. It has wires, with insulation stripped off and bent to slip over the internal battery contacts. One downside is the battery cover will have to be altered for the wires to come out, or open the shell to run the wires. I choose to solder the connections.
Did I say VERY bright? It is visible in daylight and it weighs VERY little. It is also available in Blue or multi-color, with a remote to change colors. It is infrared, like a TV remote, so you can control it in the air, but it has to be within 10-15 feet. This is a guesstimate as I only tested mine. I intend to install mine when installing my video transmitter, IOSD, antenna, etc.