If you need to travel with oxygen, I think you're allowed to bring them on the plane IF the tanks are airline approved.
Regarding the triangles:
1) the triangle that has the top flip up or down can be ordered from the dealer, try Tom Hanson at Caliber Motors (1.800.CALIBER) .
2) the older W124 triangle can be had from Rod at Potomac German Auto in St.Augustine, Florida, you will need the hold-down clip again order from Tom Hanson.
3) Even with Tom's connections, no way to get the extinguishe here from the dealer.
1988 360TE AMG w/flip-down triangle & Halon Extinguiser in center console (2.5-lbs)
1993 500E w/W124 triangle in trunk & Halon Extinguisher in Trunk (5-lbs)