Supported Frame LT210 from Banggood.com.
This universal mount can be used to hold a action cam on your Quadcopter.
Use 4 Screws (+2.5mm) to mount it to the topplate of your Frame.
There is also a lens protecting ring wich will be held in place with the strap:
https://www.shapeways.com/product/RHW6VZYEJ/lens-protect-gopro
https://www.shapeways.com/product/XSBN7DWQ3/lens-protect-xiaomi-yi
I suggest this flexible strap from www.rovaflex.at
This might also work: http://www.rapstrap.com/