Many years ago, I worked with John. John didn't say much. If he was in a good mood, he'd grunt back to you when you greeted him. John had a sign like this and I recreated it as an accessory to my grenade.
I printed the Grenade container from @Otrozone_146551 that has since been removed. It appears that he has the same model thingiverse: https://www.thingiverse.com/thing:5912403
I've included a test print to ensure that it'll fit your model, printer, settings. Not much to this print, I inserted a filament color change to contrast the signage text.
The author marked this model as their own original creation.