These were mentioned by a user in Telegram, they’re USB port type adapters that happen to have solder pads for all 4 wires on the PCB.
Soldering external power to the pads, connecting the wire to a 5V BEC, and cutting one of the pins on the back of the male plug essentially makes them USB power injectors.
The downside is it means you have 2 USB connections for every card, and they could come loose or disconnect from movement. They seem to be holding very strong but if you’re worried about it you could use them only on the ground side.
Here you can see where the pin was cut on the male USB-A plug. All you need is a pair of tin snips or strong but small scissors.