I see no purpose in getting one other than to add bling under the hood. I just checked Moroso, and they only make one for the Mustang. I am sure if you got the dimensions of it, you can figure out a way to make it fit the Focus. I have seen someone with one on their Miata. Yes, it looks nice, but it serves no real purpose. Plus he couldn't see his coolant level through the side of it. I figured if I needed to replace my leaking coolant tank, I would just go on the cheap and buy a new plastic one lol.
Completely chromed out engine bays were all the rage circa 97ish to 2000-something in the Mustang world, especially with the magazine feature cars. That's probably why Moroso cashed-in and makes them only for the Mustang.