I used one of these . It is an expansion tank that allows the fluid to travel back and forth to keep the radiator full . I prefer to do this for max cooling . I mounted it in front of the core support behind the grill .
https://www.oreillyauto.com/detail/d.../jeep/wrangler
There is so many sizes and shapes I am sure you could find something to work . Also you can spend as much or as little as you want . They will do the same thing .