This Is a weber master touch. The middle part of the grate comes out and you can put a wok, sear grate(perfect for steaks!!),or pizza stone in its place. Have you checked Amazon? Lowes/Ace hardware may also sell these grates they carry a lot of Weber items.
Look up a item called a Vortex. People are using it in Weber grills and getting some awesome chicken. I used the "poor-tex" Weber charcoal baskets they work great too!
It's pretty cool which i could make one!! Some people are getting stainless steel mixing bowls cutting bottom out with grinding wheel and making their own seems to work just as good also lol