Flat roof Trough replacement options

[Indiana Wash]

OK, my trough on my roof is galvanized steel. It has rusted apart. Do I just find a company that makes ductwork and order what I need? Has anyone found anything that comes insulated that works easier or better or lasts longer?

Thanks

 

[6t7gto]

I had mine made of aluminum and it is 22 years old. Still in perfect shape.
I insulated with 2 layers of 3/4" thick styrofoam.
Local roofing company made up my trough.

 

[Earl Weiss]

I just put ridgid Foam insulation in mine. Simple and Cheap.