Yep, I reckon that's the best thing a cone does, it stops the drips. I don't like the way it strangles the airflow though, I hacksaw 3mm off the top of mine so I can get some thicker carts in easier and get better air. It catches stray drips better too.
But this design is mainly for mods etc. Just needs an open cup. It's a simple machining job, mainly screwcutting and trepanning, you could do it on a modelmaker's lathe, a small job like a Myford. Commercially you could could knock out thousands an hour on something like a Citizen NC auto, which is what they'd use if you ordered it from China. It's three parts of course, a centre pole, a delrin insulator, and an outer part, put together in a small press or just a vice, with an interference fit.
It's basically an adapter but just 510 to 510, with a wide flange. 'Course you could make it 510 to 801 and have it do two jobs then.