In article ,
"Michael Kilpatrick"
says...
This is really frustrating. I just can't believe I can't locate a
straightforward supplier of miscellaneous rubber washers off the shelf!

All I want is a dozen washers about 15mm diameter, 1.5mm-2mm thick, with
a 6mm hole. These are for remounting some electric fans. Can anyone
please point me in the right direction?

How about cutting some from an old bicycle tyre or similar?