If you are after such a long burn time then can I suggest the Mk25 marker Marine. These produce white smoke. The details of suppliers of these would also be available from AMSA. For an even longer burn time (40 - 60 mins) try the Mk58 Marker Marine, not sure if these are available in the civil world as I have only seen and used them in the military.
In answer to your original post, here are the orange smokes that we use but they don't burn as long as you specify.
Lifesmoke Mk5
Distress Signals Day
Hope this helps...
TA