Fuse bock with solenoid

Looks like you could just drive a couple of sheet metal screws below the piece that broke off.

Trying to find a direct original fit replacement is going to be difficult. I would try removing the cracked mounting plate while leaving the components connected as they are and find a sheet metal shop to have one made from stainless using the original as a template. Might cost a few dollars but it would probably out last the coach.

I would try a local marine supply for something like this.
Blue sea

From what I can tell from the picture using the small screen on my phone, I wouldn't worry too much about identifying it. Figure out how many fuses it has and the load it needs to carry. Then buy a new fuse panel and mount a new solenoid beside it, not on it like the existing one.

Bill