Guide is WIP and will be complete once I check later.
Act 1-1: Just beside Bumblebee when the second part of the mission commences. You'll see the stand in the cut-scene.
Act 1-2: Still verifying.
Act 1-3: When you fight Soundwave - at the beginning of the battle, the stand is near an enemy bot on the right.
Act 1-4: At the beginning of the mission, the stand is found right to the left of the Autobots.