Barman Traitor Item [The chemi cloaker]

[Grek]

"I know, lets make it so he can all those horrible chems with complete impunity even when people are paranoid enough to use reagent scanners to test their drinks. But also make that thing unavailable to scientists, because it would not make sense that people whose job it is to do impossible things with chems would be able to do impossible things with chems."

That's already something barmen have - you can't see drinks on examine in glasses.