GM -- go up to www.bumperart.com
--- they have a sticker that says "Don't Honk -- I'm Pushing As Hard As I Can". It comes in three sizes and the price is different for each size.
That may be what you are looking for. I think the price is something like $4.95 and shipping/handling is $.50 each to a max of $1.00 plus first class postage.
Dave and Karen -- '02 Ultimate Advantage 36 C, 350 HP Cummins, Allison 3060 Tranny
'07 Ford Escort, Brake Master 4160, '13 Ford Edge, InvisiBrake