In one exchange, an employee told me that they didn't carry plaster washers. I informed him that This Old House told me that I could purchase plaster washers at ANY local hardware store. At that point, he told me that he thought they were in garden section and made off in the opposite direction.
After a 5 store trips, I was frustrated. Was I searching for the sasquach of home repair widgets? Is there a fictional projects tab on thisoldhouse.com that I didn't notice? No. Plaster washers, like the sasquach are out there. You simple have to either: persistently search high and low; wait patiently in one spot with a grainy 1980's video camera; or drive your wood-paneled station wagon reckless through the woods of washington state. Lacking both a video camera and a wood-paneled station wagon, I chose the first option.
The fact is that plaster washers are in EVERY Home Depot and Lowes (thanks, garden center boy), but no one knows they're there. Simply read the front of every single box in the nails/screws and aisle and you just might get lucky. Most likely, their either in the corner of the shelf just above your left foot or in a dusty box just above eye level. But, if you keep returning week after week.....