Belt label icon to easily identify bus products

In the game Dyson Sphere Program, you can assign an icon to a belt that appears at the beginning and end of the belt itself. This small feature allows you to easily identify the products passing on a bus line when it is empty (especially useful in the early game).
The icon must be the same as the product in the UI and must represent every possible product that can be transported by the belts.

This would be exceptionally useful for hooking up blueprints you did not make and wondering what the inputs and output are.