Hobby king had two small cameras perfect for this ! the wingcam, and the wingcam 2. Unfortunately the wingcam 2 doesn't show in stock anymore. The wingcam was around 50? and I paid 85 for the 2 version. but the resolution was SO good! I used it for years but something finally went wrong.. it had been in about 5 crashes and had gone 160 mph on a jet ! Most of the footage on my youtube taken the last few years is with the same camera.

Here is some footage taken with the Wingcam 2.

https://www.youtube.com/watch?v=FZeN8Ei3orw