If you already have a Cylinder and MH Regulator, you can order just the O2D2-2G unit kit. The MH EDS O2D2-2G Pulse Demand Oxygen Delivery System is the only single unit, portable, two-place oxygen system currently available for general aviation.
The O2D1-2G kit comes with (2) AA batteries and 2 cannulas (1 Standard and 1 Flare-Tip) and 1 face mask in a handy carry bag. General info on oxygen systems: https://lrb.no/downloads/mhbrochurerev6.pdf
The XCR series of regulators are essentially single-outlet. These regulators feature the SMC quick-lock system for the 4 mm. and 6 mm. polyurethane tubing. Available with a built-in cylinder pressure gauge. These XCR Regulators are DIN-477