Weber offers it as an upgrade in the build your own Master Touch. I am was able to find the 26" SS GBS but no 22"
I called Weber Customer Service and asked them for the part number for a SS GBS cooking grate for a 22" kettle. The CS rep put me on hold for a couple of minutes and came back on giving me the part #65057. He quoted the price as $82.40. I tried searching that part number on Weber's website but nothing comes up. I then tried Googling the part number and it came up under Appliance Factory Parts website as a special order part with a price of $94.36. It does list is as a SS GBS grate for a 22" Weber on the Appliance Factory Parts website.
It's pretty common for not all part numbers to come up on Weber's website. I can also understand the price difference between the $76 Weber build your own price and the $82.40 stand alone price by Weber. Very common pricing when dealing with packaged pricing.
If you wish to order you would have to call Weber Customer Service at 800-446-1071 (option 1) and order part #65057. I also double checked my Weber parts list I forgot I keep and in fact found the SS GBS for a 22" listed as #65057. I must have done the research once before. Dohhhooooooo!
Hunsaker also offers a 22" SS GBS cooking grate for $109 (link below)
https://www.hunsakersmokers.com/collections/replacement-grates/products/premium-stainless-steel-food-grate-for-26
Hopefully this helps.................