Get some Gorilla Glue.
Squeeze Gorilla glue into the hole where your power supply leg use to be.
Squeeze more Gorilla glue onto the end of your broken off leg.
Try not to go crazy with the Gorilla glue.
Take the little broken leg and stick it back into the slot, in the “out” or “open” position.
Use Scotch tape to secure the leg in position.
Wait for 12 hours.