I have looked into these and there are 2 or 3 out there. But it may be a solution for a problem that no longer exists. Many who use them have engines from the 60s and 70s. And there are some expensive ones for certain diesel engines.
Use the recommended coolant and change it according to the manual. And if you use DexCool, keep an eye on it for the intake manifold gasket failures and in a few cases, radiator caps.
Were I to buy one, I would get one that goes in the heater hose, not radiator hose.