1. There might be a part available from Mazda 2. Cut out parts from a breakers. I would think, Mk1 or Mk2, it makes no difference. At the very least, you are looking for something to provide a reference. 3. Source Escort part (Mark??), which seems like it might be fettled to fit (smashed to shape).
This is an unfortunate situation as no repair panel seems to be readily available.
A good fabricator should be able to fashion a part with relative ease but will need a pattern to work to.
In your position this will probably involve a trip to a scrapyard with a grinder to cut off the inner panel from a car with more material to work with than yours.
Most cars are scrapped because of corrosion in this area so unlikely but not impossible that you will find a re-usable section down the yard.