Heat exchanger - 10hp diesel

[Stuart 28-2]

My heat exchanger is dripping water pretty badly when the engine is running. I'm somewhat sure it's a crack in the casing. Can anyone suggest where I might purchase a new one, and any time saving tips for the search?

 

[G Kiba]

I remember someone posted https://www.mrcool.us/. I have no knowledge of this company but they look good!