If I was in that much of a bind, I would go buy the 22" kettle charcoal grate from wherever, cover it with regular foil, and then pierce through the foil so heat and smoke can circulate through but the meat still doesn't touch the bare metal. I wouldn't cook on the charcoal grate itself, new or not. Even if you use it in this manner only one time, you're still going to probably replace your charcoal grate at some point down the road, and you'll have one when you do.
On edit: Well, that grate doesn't fit the WSM as a charcoal grate, but if you have a 22" kettle...