Earlier this year I brought back from Germany a factory MB fire extinguisher and bracket from a 126 coupe for my 560SEC, in my luggage on board an American Airlines flight. There was no problem and certainly my baggage was x-rayed multiple times before and during transit (flight transfers).
I purchased it from Marc Van de Velde in Belgium, who runs the largest MB wrecking yard in Europe. It's about 3 hours' drive north of Paris.
Attaches in the factory stock location directly in front of the driver's seat.
"Just Say No to Ü-R-O [parts]"