Hopefully the plastic actuator is one piece with the switch, and not an addon from the laptop people,
I had a problem, with a power button missing, the plastic piece with the power sign on it, couldnt find it anywhere online, and well ASUS gave me one option, send in for repairs, they kept saying they dont sell parts, but i would end up paying for it anyway, i even offered $20 for it, they wouldnt budge
But if it looks like plastic that broke off the main body of the switch, then you can find an exact replacement, be sure you make sure and order the exact one, as digikey and mouser have many selections, id suggest getting the calipers out, to take body size measurements, so you do get the exact one and dont make a mistake and waste time in ordering, but i also suggest ordering a few different ones that are similar, shipping will probably cost more then a few of these parts.