Comparison of some InMoov cameras and relative sizes
Here is a comparison of the relative sizes of webcams and two of the InMoov eye mechanisms. The webcams are, left to right, Ubisoft Motion Tracking camera ($10 on eBay, very small but only 640×480. It has a very wide angle screw-on lens, though, that might work with other cameras. Great camera for $10.
2nd is the Hercules HD Twist. Almost as small as the Ubisoft but 720p resolution. Note that this camera is oriented vertically. No threads for lenses. Includes audio. Several Thingiverse eye mounts including Gael's gen 2 mounts are designed for this camera. (bottom right in image) I got 2 from the UK for $45 each. Next is the Hercules HD720P. It is a little wide but can be made to fit into Gael's mount. I paid $15 for it on eBay. The square camera with the ribbon cable is a Raspberry Pi camera board. This fits inside the giant eyeballs in the mechs posted by Monnerby and Bob Houston (bottom left in image). This is a great 1080p camera for about $30, but you have to connect it to a Raspbery Pi, so I think you will need to go all-in on Monnerby's head mods. The last camera is a 480p camera I bought on eBay for $5. Note: Do NOT buy any cameras that have infrared LEDs in them as they typically cannot be removed and won't fit in an eye mechanism. I included a set of human-sized 25mm eyeballs that I use in animatronics for comparison.