We also have a U Line separate Ice maker in Our Rig. I agree that the various Campground water sources are frequently "Off"!
There is nothing particularly special about the Mechanical parts used in this under counter device. The Ice cubes are formed in a Universal type of machine that can be found in most refrigerators that have ice makers built in, and purchased as an add on for many others. I have a couple of them on a shelf in My Garage that I removed from some Old Fridges that had outlived their usefulness.
Anyway It is a simple matter to Zip tie Up the Refill sensor Arm so that it remains shut off . Then just use the Box as a small Deep Freeze.
The Water Supply Hose should have a Shut Off Valve which needs to be closed to prevent any accidental production of unwanted Ice Cubes!
You must remember that this unit only works on 110 so you can't use it while dry camping unless You have an inverter!