You can get power from either. You can solder to the connector on the motherboard, the traces that lead to the speaker connector, the connector itself, or the speaker. And you can definitely do the trigger mod without a drill. You can either:
A.Place the leds next to the trigger, just make sure you do it so it does not interfere with the movement of the trigger
or
B. Poke your trigger with your soldering iron, and clean your tip and re-tin it.