I went looking for a pic of the old 150mm PVC pipe on roofrack sorta thing plumbers use, to stick here as a p!sstake as its basic and been used for decades.
First result - all the Rhino rack stuff. They want $75 for a damn screw on end cap




You could build the whole damn contraption including brackets and tube, for less than that.
Seriously, $75 for a screw on end cap, for standard 100mm PVC stormwater pipe.
Surely no tradie would buy it.

So, student1..... for your project design a system to undercut that by 90% and you're in.