604, next time you're in DC I will buy you a beer! I just called Weber with that stock number, and they have those sweeps in stock for like $13, with free shipping to boot. Cheaper than the conventional aluminized steel, I believe! So there is one happy Weber nerd at this end of the internet today. Really appreciate your help, and the hint that yours came from the Mothership. ;-)
Thanks too to Winz for identifying that mysterious stock number.