Welcome Chuck, and sorry to hear about your quickly escalated situation.
You probably won't find a used door unless you happen to luck out on Craigslist. Due to all the labor required and relatively cheap components, RVs are generally not parted out like cars.
I would give Bontrager's RV Surplus a call with those dimensions. They should have one. I'm not sure if they would ship it, everyone I've known has just gone there:
If they don't work out, you can check with All-Rite, they may either have one in that size or can build you a custom one. Chances are it's a stock size:
RV Compartment Doors | RV Compartment Doors For Sale - All-Rite
In the mean time, I would recommend taping up over the opening so no water does get in. Since it's cold now, it would take an even longer time to dry everything out. Use a trash bag and some tape if you need to. Instead of duct tape, which can leave some nasty residue, I've used white face Gorilla tape. The adhesive backing is still gray, but it doesn't seem to leave residue as easily. It will over a long time (like all winter), but for a short term cover, it should be fine.
Yes, Sunline started making a lot of models without windows over the bed- apparently enough people complained about condensation dripping down in cooler weather. Personally I wish it remained an option, but they went to the fancy headboards instead.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR