The carts were sold exclusively by others. I don't know whether Weber manufactured them though. This setup does have a name. They are called "Woodwards".
hmmmmafter a bit more digging, i wouldn't be surprised if WoodWard actually made ALL the iron carts (even the Weber branded Sevilles)it would explain the wheels matching...plus Weber likely didn't have the manufacturing equipment to handle wrought iron.search for "woodard wrought iron furniture vintage" and a lot of the furniture is VERY similar in style and character and ornateness to the white Weber Seville.