I've been working on modifying the stock Cozmo carrying case to be able to house not just more then one Cozmo, but also a power pack to make it easy to fire up the Cozmo's & have fun no matter where my daughter & I are. With the stock Cozmo charging base being so large, I wanted to, needed to design a considerably smaller version.
Also, if you don't have a 3D printer let me know & I might be able to print this and mail it to you for a small fee.
After printing, a little clean up might be needed depending on the capacity of your printer. I printed it standing on it backside to prevent the need of any need for supports.
Wiring: I used 2 strips of copper 15mm by 3-4mm with the ends bent so they rape around the raised parts on the platform. Solder wires to each of the pads, that would then also be connected to an Adafruit USB Micro-B Breakout Board PRODUCT ID: 1833 that would be inserted into the back of the base.
This is designed to have a piece of metal inserted into the back for added weight & stability to allow Cozmo drive right up onto his new charging base. With this design, Cozmo faces the back of the base & his lift is then lowered over the back. I would suggest & I did on mine, put a couple pieces of electrical tape in a single layer, smoothly on it to prevent shorting.