All that stuff wouldn't fit behind the seat of my truck. But I carried a spill kit.
Eye wash kit is good, but also have chemical goggles--particularly important if you carry any concentrate chemicals. I had sunglasses with liquid side shields.
Cell phone would be handy. Even if you have to pay your employee for each call he makes to you.
Essential, and probably required by law, liquid soap dispenser and a sprayer filled with wash water only, to clean the hands.
If space is tight--maybe use duct tape and tape the liquid soap to a 1-quart hand sprayer filled with clear water.
Anybody else--what is the best way to carry soap and water?