Just figure out what breaker is running the upstairs bedroom, and swap out the single breaker for a dual breaker. You will have to run wire, & install an outlet in the attic. Run attic on one side, and bedroom on the other side of the breaker, then each both will have their own breaker and you won't have to piggyback off a single breaker. Or you can do like many people do, and just run wire off the breaker that's running the bedroom, personally, I don't like to piggyback, I swapped out a couple single for duals because they had more than 1 line hooked to a single breaker.