HELP WANTED - how to make d shaped tubing?

[Toolmaker51]

The initial D shape I'd begin by drawing through a succession of shaped rollers.
For the record; round, square and rectangular tube is formed out of flat stock.
For the bend, there a friendly tube bending [exhaust] shop nearby. I'm willing to bet a linked mandrel will do this.
Half the bend desired is called 'hard way', where apex meets the flat of D. Hard way refers especially to angle iron, C-channel, flat stock etc, when the bend stretches outside of perpendicular edge.

Homemade tools made with Harbor Freight tools
Post #15 Harbor Freight Bender mod for on-edge [hardway] forming.