GI is usually AC, mainly to control the light intensity from the CPU, so it is not a good option to power your laser or other mod that needs DC. You can get 6v DC from some insert lamp, for example from the lamps in the slingshots or directly from the power supply board.
To get 4.5v for your laser, you can add two 1N4004 diodes in serial to reduce the voltage from 6v to 4.5v DC. It is the simplest and most economical way.