Made this mod for Cozmo after getting inspired by Just Baselmans Vector Lego Wheel Mod.

This is entirely 3D printed, though for assembly some super glue will be required for the wheels.
The tires are supposed to be printed in TPU. Though I added (No Lip) variants of the Rims which could have the PLA wheels slot in, they'd just have to be glued in to avoid them slipping about.

I printed the Rims in PLA and Hooks in PETG. 
The hooks slot into the holes inside the Rim, facing outwards (see last picture) and need to be glued in. The reason it's done this way is to avoid the latches breaking at layer lines, making it far stronger.

Cozmo doesn't fit into his charger with the wheels, so I printed a simple new low profile charger for it. You can simply unscrew and remove the cable with the charging board from the old charger and slot it into the new one. (the screws in the original charger are under the 2 rubber pads in the back). The charger is heavily Work in Progress but functions!

Since Cozmo doesn't really have areas to make accessories snap in, some double-sided sticky tape will be required for the spoiler and the ears, though they are optional.

The wheels also fit Vector, though his charging conditions are far different and more complex. I added the WIP files in case anyone wants to give it a shot, though I found that with the wheels Vector would usually fail to park properly, as well as the design probably needs adjusting to accommodate that.