The truth is that we’re a niche hobby here. Our outward enthusiasm is what brings things like the Vortex to market. And yes, our same creativity towards mods and tweaks will lead some of us to make Poortex’s and other accessory copies that partially are parasitic. That’s the bargain manufacturers (including Weber of course) make to have our kind engaged.
I think overall we as a group strike the proper balance, meaning the majority do in fact buy the original thing for reasons of practicality.
All of which is to explain my comment better: I get the OP’s desire to make (or have made) his own version. Examples of that sort of thing are everywhere here.
I mean, it’s just a damn cone. But as noted, it’s a SS cone for not huge money, whereas aluminum flashing is closer to a waste of time. And we’ll always herald the great and try to steer a Grillfella to better solutions, honestly.