On the pcr you just unscrew the sleeve, remove the indicator and spring, then screw the sleeve back in, that will leave a small hole similar to the hole that is used as an indicator of sorts on the M&P series. I haven't tried that yet but the small hole, useable or not isn't a bit deal. I'm not familiar with the 97 so I can't speak for that model.
Just took a look at the 97 parts schematic and it looks like you should be able to remove the nut,spring, and indicator and then reinstall the nut alone and just be left with a very small hole. I'm just guessing here as I've never actually seen the gun.