There are several options out there. Your unit should be double din. From talking to Crutchfield about options to replace what came in this trailer (Furrion) there weren't many that were RV specific. Jensen, iRV and Furrion come to mind. And on that topic, if I were you, I would avoid anything with Furrion on it.
I replaced my last one and I looked for something that didn't require me to completely rework the woodwork. Jensen makes a couple of units that might hopefully just go right back into the same holes you have. You also probably need to just pull the head and see what that cutout looks like. I suspect it is a full cutout. This trailer came with a Furrion double din but only 1/2 of the wall is cut out behind it. It has a double din faceplate/controls but only uses a single din cutout.
Here's a link to a iRV unit on Amazon that has measurements on the front:
They also have Jensen units.