It is normal for rental owners to increase minimums during Christmas week.
Think of what you are asking here. With a checkout on Christmas Day, that means cleaners have to rush, on the holiday, to get the room or rental ready for a check-in.
Christmas is a big family holiday here, and people do not work on it unless it is absolutely necessary. Nor would any rental wish to lose the opportunity to have it rented Christmas Day.
My suggestion would be to try to rework your plans.
If you are finding it impossible, most likely it is.
If there were a puka (hole) in the calendar for one night, close to the date, someone might open up a one night stay, but only if they can arrange for cleaning on Christmas.
I don't see anyone mucking up the holiday availability by blocking Christmas Eve out for a one night stay as of July. If they do, they are not very business smart.
Sorry to be negative, just want you to understand what is in play here. Wishing you a good solution.