Go to the power plant, then go to Cerulean gym, and there will be a rocket guy. He will run away. He will be on the bridge. Kill him, then go to the plant, after he gives you the piece of machinery. You will get praise and most likely nomz.
Power Plant
you have to have completed the power plant mission and he will be outside the power plant on the left
See below
The grass in Kanto by the Power Plant.
it is i the kanto region in soul silver after you defeat the elite 4
Battle Misty
At the Power Plant.
I don't know when but after a while the power plant
start by heading north and taking route 10 to the power plant
It's in mistys gym
it's in the gym where u vs. misty
you go to the cerulean gym by the floaties on the left after take it back to power plant