I found these folks in the Czech Republic through eBay and then started dealing directly with them through their website. They offer EVERYTHING that a Weber could want. So far, customer service has been exceptionally good and I'm awaiting my first shipment of genuine, made in the EU, Weber parts to rebuild my 40 DCOE carbs. They may not have the best pricing you might find on Part X, but they have the whole enchilada and things will tend to even out.
You can also buy complete DCOE carbs (with air horns) through them for what I think is a great price; currently $323 as of October, 2021. And, you can specify the jetting that you want. I suspect they will be very amenable to air horn changes too.
Of course, there's an international shipping charge on everything, but still. . .