Hmmmmmm. Custom assembled but I wouldn't think custom made.
There seems to be enough pre-made parts of all shapes and angles to accommodate what needs to be designed here.
Just a few examples from my first search.

Of course, I may be greatly oversimplifying and I'm probably the type of customer these contractors really hate for doing so. Perhaps the 90 degree fitting with the deflector in it but I can't see that being complicated or hard to find.

With great power comes Awesome irresponsibility.