Interior trim pieces are one of the most difficult to find. Many times the manufacturer made changes in trim for each year so there was at least some difference from one year to the next year. Plus you need to find the correct body style. A two door model won't cut it. Then to get a color match in good condition makes the hunt rather difficult.
With that said, the 1978 to 1980 four door and four door wagons may work. The Mercury Zephyr likely has different trim scheme however it may be worth a look.
What you might explore is asking E-bay sellers like this one if they have that type of thing.
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