Here's a couple shots of the charger plug assembly that I've put together.
Basically I just cut a disk out of aluminum plate, carved a hole to match the back end of that plug and then fixed it into place by putting the plug on one side of the plate, and the stress relief clamps that the plug uses on the other side. Once I screwed them down into place the plug is secured and doesn't move.
This is the assembly in place under the gas cap. Seems like the most logical place to put it after all. I still need to figure out how I'm going to affix a switch in that compartment so that when the door is open, the Zilla controller is deactivated and the car won't run. After all, I don't want to mistakenly drive off with the plug connected.