We get asked fairly often about filling sodastream tanks. Our partner at Carbonics has tried for years to find the right adapter to fill these. We have just recieved these from KegLand out of Australia, at this juncture we do not know yet how effective they are. We ask that our customers apply caution when using these units.
Here is a description from the manufactuter: "Perfect for those who aren't interested in having to swap their empty Soda Stream cylinder every time. Attaching this adapter to your Co2 tank allows you to fill US/CA Soda Stream Co2 Cylinders. The adapter threads onto a male CGA320 Inlet and provides a Soda Stream Cylinder Tr21-4 connection. The manually controlled bleed valve allows you greater precision when it comes to filling your Soda Stream Co2 Cylinders. For best results you should use a 20LB C02 Tank with a syphon tube installed, or put your CO2 tank upside down."