Ok .. I've been down that road before, here is what I did.
I assume your talking about the lower grate, get a cheap standard 18 grate and that can work.. with a little help from your friends.
Take the bottom bolts out from the straps and replace them with 1/4-20 size carriage bolts (flat head with the square under the head) and install these backward with the head on the inside. Get short threaded ones or cut them down to fit.
Then I used (acorn) nuts. Smooth closed nuts that the bolt does not go through. Looks better in the end.
Doing this way will give you JUST enough room to squeak a standard 18 grate down in to place .
I don't know why Weber did not do it this way?
Hope this helps you!
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