Weber kettles are amazing and the Weber Smokey Mountain bullet smokers are, dollar for dollar, the absolute best smokers available.
These great grills and smokers deserve equally amazing internal components. Here are a few options that I have made available through my Quality Grill Parts product line on Amazon.
For 22.5 inch Kettles and Smokers
(This is a 17 inch grate that can also be used as the lower cooking grate on an 18.5 WSM.)