You should be able to find zerex G-05 in most auto part stores (Advance, Autozone, Napa, etc.). Walmart might even sell it. If you yourself can't find it... ask someone in the store.

FYI, some Walmarts carry Mopar fluids. So you might be able to find it there.

You'll need 1 gallon then add water to fill up the rest of the system.