The top grate is the same one you'll find at most hardware stores for the 18.5" kettle grill. It's the bottom grate that must be ordered direct from Weber due to it's odd size and lack of handles.
I'm going to buy an extra top rack after seeing another thread in this forum - turn 1 rack over and rotate 90* and just like that you've got another rack for ribs at the top of the bullet. The only drawback to my 18.5" WSM is the ocassional lack of rib space (I like to keep them laid flat).