You got to knock, and knock agian if needed.
I have picked up a 14.5 SMC, red Smoky Joe, a gas kettle and a avocado 18.5 by knocking on doors. Some were easy, some took over a year to get. Some I never got.
The best part is that they did not end up in a landfill some where. Just think about what/who is best for that rare, collectable classic Weber. Some people would appreciate it going to a good home.
There are no laws agianst knocking on a door, at least the first time.