I want to clean my AC evaporator coil in the attic. I did some reading on the web about Triple-D and NU-CALGON and such, but where can a regular person buy these product?

I want to clean the coil in-placed with minimal rinsing with water. Does anyone know which cleaner I should use? And where do I buy them, preferably in the store?

I'm trying to extend the life of my AC in the Texas HEAT.

Thanks