Need mixing valve with ratio control

I didn't think this would be so difficult to find, but I am in need of a mixing valve that allows me to control ratio. I need to set it up on a barrel of concentrated cleaning solution. Ideally it has water and the chemical both coming in, and then mixing together at a 2:1 ratio in the output. It's for an industrial setting so needs to be fairly accurate. Can anyone think of what it is I need? I've looked at the thermostatic valves but they don't appear to have the type of control I need. Thanks for any help