This is a simple hand-held mount that we designed in 2014 for a pair of Canon PowerShot A4000 cameras to capture synchronized stereo images or video.
The camera mount is our own design, holding a pair of A4000 so that the stereo baseline approximates that of human vision. The cameras can be screwed-in via their tripod sockets, or can be secured using tie straps, but they actually clip in well enough for normal use. The grip (which was derived from Thing 62606) is hollowed to accept a standard 9V battery, momentary switch, and dual-port USB connector (to which we wired a 7805 voltage regulator). Thus, the wiring in the grip allows for a regulated 5V to be supplied to both USB port connectors when the button is pressed, and CHDK allows the cameras to be triggered at precisely the same time by detecting that 5V signal on the camera USB ports.
The reason we didn't post this design earlier was the awkwardness of using the 9V battery and regulator as the 5V source -- a rechargeable USB battery would be the correct answer now. However, this design is discussed in Lessons from design, construction, and use of various multicameras at Electronic Imaging 2018, so, here it is....
PLA works fine. The two pieces print separately and slide together after the battery and wiring have been installed in the handle. It's an easy print except for the span over where the dual USB socket goes -- you might want some support for that, although some sag really just helps the USB socket fit more firmly.
Installing the 9V battery is easy, but fitting the switch, 7805 regulator, and dual USB socket into their places isn't as easy. In any case, you'll need to wire them together before putting them in. A little hot glue, or shaping of the PLA using a soldering iron on the inside, can be used to firmly set the switch and connector in place.