Has anyone thought about matching the hole that's in the new WSM's and using a grommet from one of them? Can you buy just one of those grommets?
I checked ereplacementparts.com and did not see parts listings for the newer cookers. You might be able to get the parts from Weber but their CS is notorious for refusing to sell anyone parts for a cooker they cannot prove they own.
Then it would just be a matter of doing a good job with a hole saw. If I were going to do that, I might be inclined to cut the hole a little undersize and then opening it up with a Dremel grinder.
I remain happy with an ordinary brass grommet. Cheap, easy to find and easy to drill an appropriate hole.