These have started appearing on the back of First buses.
Rumour has it that Lothian has been planning stickers saying "Do not pass on the left" - possibly even in CAPITALS.
Concerted effort by the police and council (inc Cllr. Mackenzie) seems to have caused a re-think.
It might be simplest to order some stickers like the one above, but LB will probably come up with their own version!