Check out RunCam. They have a broad selection and are sold on ebay, amazon, new egg and just about any other site you can think of. They have a great rep for being rugged, inexpensive and have a sharp picture. I just got, but have not used yet, the RunCam SKY 2. It is a HD board cam that I will run thru a 5.8 ghz Tx to a 5.8 ghz Rx to a mini dvr and to my monitor. The idea being I will be able to record exactly what I see while flying FPV without having to use a separate camera. Still refining my mount idea for it. For your gimble, I don't see why just about any of them wouldn't work mounted down or up. Particularly the 2 axis ones. Just make sure whatever camera or device you are using will fit the mount. I have seen a huge variety of motor driven and servo actuated mounts all over the net. It may be as simple as picking a favorite vendor and choosing one of their offerings.