Mine came from the hardware store. They are just a shade under 1/2 inch tall. (15/32"). They are conical and made from rubber. They compress just a tad when the box is closed so that there is no vibration noise from the box. And they are STOOOOOPID cheap compared to what they want at a dealership.
I dream of living in a world where chickens can cross the road and not have their motives questioned.
Be kind. If for no other reason, it will confuse the daylights out of people and make them wonder what you're up to.