Google Ford dealerships in the UK (or any UK Ford "mains" dealer) and email their parts departments to see if any NOS hubs are available for Mk 1 Fiestas. If you have no luck, try Burtons, a great UK Ford aftermarket house.

Brit merchants are very helpful and accomodating.

There are probably UK-based Fiesta owner groups and websites that can also help. The Fiesta was (still is) a popular "clubman's" racecar in the UK.

Finally, do you have the Ford North America part number for the Hub? Did you check Partsvoice.com?