My fiance's luggage got destroyed on a recent BMI flight. It was a small SAMSONITE case with dimensions designed to be taken into the cabin with wheels and a pull out handle.

The two zip pulls were fastened with a padlock and it seems the padlock got caught in a conveyor belt and the zip pulls were wrenched from the zip. Alas, I can't fit the zip pull back into the 'zip teeth'. Doesn't look too damaged though, Samsonite made a good sturdy case there.
It could mean that the zip will have to be replaced if it can't be fixed.

Does anybody have any ideas about the best way to go about this?

The case is quite old and way past it's warranty, however, it does have a great deal of sentimental value as it belonged to his mother who died last year.
I'm based in London, will be travelling to New York for a week at the start of Novemeber, I'll be in Tokyo at Xmas and it looks likely that I will visit Beijing and Madrid sometime next year.

If anybody knows any places at these cities that could help that would be really helpful.
Thanks!