Jon, the door on the freezer of my 92 Scamp
also broke a few years ago and I was fortunate to find someone here who had decommissioned the same fridge
to send me the one off of their fridge
. It worked but it never really closed as well as I would have liked. That one broke just this past week-end and funny enough without the two hinges the door actually closes and stays closes better than it did with the tiny plastic built in hinges on it! I just stuck it over the opening & it stayed in place and fully closed for about 100 miles of travel a few of those miles where over a bit of a rough road.
I actually really LIKE your ideas of using a couple of small magnetic on it - not sure I would use a latch although having to take it completely off when opening as I do now may not be the best.
I have considered adding a couple of really small plastic or metal hinges to it - was going to the marine supply shop today to see what they might have - just worried about screwing them into the main freezer compartment side - may just glue them on it rather than screw them on.