Lumenier QAV210 HD Camera mount, Is designed for clone frame, but I suppose it'll work for the real models to.
The HD Cam overhangs the frame a bit, I did this because I have long batteries which wouldn't fit if I didn't use a overhang. Though this gives a small problem that the FPV cam can't go higher than 20°/25°. But this shouldn't be too big of a problem if you fly with your cam at 20°/25° anyways. Though the FPV cam can go higher than 30° when you use the 30° mount.
If you'd like to see any changes, tell me in the comments and I'll be able to super quickly modify the part.
As you want the mount the be as light as possible, I'd recommend to print the part at a 20% infill. This is still strong and light enough.
You need to use supports for the bottom overhang where a zip tie or velcro would go.