Yeah, I got lucky and mine came with the original pan. It sounds like they may be doing another order on ash pans towards the end of the summer. You can use a standard 18" pan off Amazon or wherever, it just won't have that original look.. You can post a wanted ad in the members section as well. You never know.
I don't know how much you've looked at yellow's, but one reason so many people like them is because they change color to an orangish when they get hot. You can see it starting to turn in my pic above on the bottom of the grill.