Help finding powerup? Main Sector, locked elevator

[mehe]

So I'm at the end of the game where she's gonna get Adam's helmet. I've just stumbled to the locked elevator, the room down from the second door that requires a power bomb to open. And there's a powerup charted on my map on the right side of elevator and I've scaled up and down the whole thing yet don't know where it is!!!!!!!!!!!!

[Mewtwo]

You have to kill the final boss before you can get that one. It'll then take you down the elevator, and at the bottom theres a little tube to go through, in which theres the expansion.

[CapCom]

Yeah, that one's a pain. It must have taken me a half-hour or more to find it.

[Plas Durock]

You have to kill the final boss before you can get that one. It'll then take you down the elevator, and at the bottom theres a little tube to go through, in which theres the expansion.

Actually you can get them all before fighting the final boss. (phantoon) You just have to get that before the credits role.. other yeah you have to beat phantoon to get it.

[Heavenlyhero]

Screw attack down once you bomb the elevator and look for a vent to roll into on the left side as you screw attack/space jump down. Once you roll through it, it will lead you to the missile tank. If not, try the right side. Pretty sure it's the left side vent, though.

You can get it at the beginning of the game. Just jump up into the little tube to the left the first time you get to the main elevator, and the missile is yours.